The sane_reclaim() helper is supposed to return false for memcg reclaim
if the legacy hierarchy is used, because the latter lacks dirty
throttling mechanism, and so it did before it was accidentally broken by
commit 33398cf2f3 ("memcg: export struct mem_cgroup"). Fix it.
Fixes: 33398cf2f3 ("memcg: export struct mem_cgroup")
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is merely a politeness: I've not found that shrink_page_list()
leads to deadlock with the page it holds locked across
wait_on_page_writeback(); but nevertheless, why hold others off by
keeping the page locked there?
And while we're at it: remove the mistaken "not " from the commentary on
this Case 3 (and a distracting blank line from Case 2, if I may).
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
reclaim_clean_pages_from_list() assumes that shrink_page_list() returns
number of pages removed from the candidate list. But shrink_page_list()
puts back mlocked pages without passing it to caller and without
counting as nr_reclaimed. This increases nr_isolated.
To fix this, this patch changes shrink_page_list() to pass unevictable
pages back to caller. Caller will take care those pages.
Minchan said:
It fixes two issues.
1. With unevictable page, cma_alloc will be successful.
Exactly speaking, cma_alloc of current kernel will fail due to
unevictable pages.
2. fix leaking of NR_ISOLATED counter of vmstat
With it, too_many_isolated works. Otherwise, it could make hang until
the process get SIGKILL.
Signed-off-by: Jaewon Kim <jaewon31.kim@samsung.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
If transparent huge pages are enabled, we can isolate many more pages
than we actually need to scan, because we count both single and huge
pages equally in isolate_lru_pages().
Since commit 5bc7b8aca9 ("mm: thp: add split tail pages to shrink
page list in page reclaim"), we scan all the tail pages immediately
after a huge page split (see shrink_page_list()). As a result, we can
reclaim up to SWAP_CLUSTER_MAX * HPAGE_PMD_NR (512 MB) in one run!
This is easy to catch on memcg reclaim with zswap enabled. The latter
makes swapout instant so that if we happen to scan an unreferenced huge
page we will evict both its head and tail pages immediately, which is
likely to result in excessive reclaim.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mem_cgroup structure is defined in mm/memcontrol.c currently which means
that the code outside of this file has to use external API even for
trivial access stuff.
This patch exports mm_struct with its dependencies and makes some of the
exported functions inlines. This even helps to reduce the code size a bit
(make defconfig + CONFIG_MEMCG=y)
text data bss dec hex filename
12355346 1823792 1089536 15268674 e8fb42 vmlinux.before
12354970 1823792 1089536 15268298 e8f9ca vmlinux.after
This is not much (370B) but better than nothing.
We also save a function call in some hot paths like callers of
mem_cgroup_count_vm_event which is used for accounting.
The patch doesn't introduce any functional changes.
[vdavykov@parallels.com: inline memcg_kmem_is_active]
[vdavykov@parallels.com: do not expose type outside of CONFIG_MEMCG]
[akpm@linux-foundation.org: memcontrol.h needs eventfd.h for eventfd_ctx]
[akpm@linux-foundation.org: export mem_cgroup_from_task() to modules]
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Vladimir Davydov <vdavydov@parallels.com>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
If a PTE is unmapped and it's dirty then it was writable recently. Due to
deferred TLB flushing, it's best to assume a writable TLB cache entry
exists. With that assumption, the TLB must be flushed before any IO can
start or the page is freed to avoid lost writes or data corruption. This
patch defers flushing of potentially writable TLBs as long as possible.
Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
An IPI is sent to flush remote TLBs when a page is unmapped that was
potentially accesssed by other CPUs. There are many circumstances where
this happens but the obvious one is kswapd reclaiming pages belonging to a
running process as kswapd and the task are likely running on separate
CPUs.
On small machines, this is not a significant problem but as machine gets
larger with more cores and more memory, the cost of these IPIs can be
high. This patch uses a simple structure that tracks CPUs that
potentially have TLB entries for pages being unmapped. When the unmapping
is complete, the full TLB is flushed on the assumption that a refill cost
is lower than flushing individual entries.
Architectures wishing to do this must give the following guarantee.
If a clean page is unmapped and not immediately flushed, the
architecture must guarantee that a write to that linear address
from a CPU with a cached TLB entry will trap a page fault.
This is essentially what the kernel already depends on but the window is
much larger with this patch applied and is worth highlighting. The
architecture should consider whether the cost of the full TLB flush is
higher than sending an IPI to flush each individual entry. An additional
architecture helper called flush_tlb_local is required. It's a trivial
wrapper with some accounting in the x86 case.
The impact of this patch depends on the workload as measuring any benefit
requires both mapped pages co-located on the LRU and memory pressure. The
case with the biggest impact is multiple processes reading mapped pages
taken from the vm-scalability test suite. The test case uses NR_CPU
readers of mapped files that consume 10*RAM.
Linear mapped reader on a 4-node machine with 64G RAM and 48 CPUs
4.2.0-rc1 4.2.0-rc1
vanilla flushfull-v7
Ops lru-file-mmap-read-elapsed 159.62 ( 0.00%) 120.68 ( 24.40%)
Ops lru-file-mmap-read-time_range 30.59 ( 0.00%) 2.80 ( 90.85%)
Ops lru-file-mmap-read-time_stddv 6.70 ( 0.00%) 0.64 ( 90.38%)
4.2.0-rc1 4.2.0-rc1
vanilla flushfull-v7
User 581.00 611.43
System 5804.93 4111.76
Elapsed 161.03 122.12
This is showing that the readers completed 24.40% faster with 29% less
system CPU time. From vmstats, it is known that the vanilla kernel was
interrupted roughly 900K times per second during the steady phase of the
test and the patched kernel was interrupts 180K times per second.
The impact is lower on a single socket machine.
4.2.0-rc1 4.2.0-rc1
vanilla flushfull-v7
Ops lru-file-mmap-read-elapsed 25.33 ( 0.00%) 20.38 ( 19.54%)
Ops lru-file-mmap-read-time_range 0.91 ( 0.00%) 1.44 (-58.24%)
Ops lru-file-mmap-read-time_stddv 0.28 ( 0.00%) 0.47 (-65.34%)
4.2.0-rc1 4.2.0-rc1
vanilla flushfull-v7
User 58.09 57.64
System 111.82 76.56
Elapsed 27.29 22.55
It's still a noticeable improvement with vmstat showing interrupts went
from roughly 500K per second to 45K per second.
The patch will have no impact on workloads with no memory pressure or have
relatively few mapped pages. It will have an unpredictable impact on the
workload running on the CPU being flushed as it'll depend on how many TLB
entries need to be refilled and how long that takes. Worst case, the TLB
will be completely cleared of active entries when the target PFNs were not
resident at all.
[sasha.levin@oracle.com: trace tlb flush after disabling preemption in try_to_unmap_flush]
Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Nikolay has reported a hang when a memcg reclaim got stuck with the
following backtrace:
PID: 18308 TASK: ffff883d7c9b0a30 CPU: 1 COMMAND: "rsync"
#0 __schedule at ffffffff815ab152
#1 schedule at ffffffff815ab76e
#2 schedule_timeout at ffffffff815ae5e5
#3 io_schedule_timeout at ffffffff815aad6a
#4 bit_wait_io at ffffffff815abfc6
#5 __wait_on_bit at ffffffff815abda5
#6 wait_on_page_bit at ffffffff8111fd4f
#7 shrink_page_list at ffffffff81135445
#8 shrink_inactive_list at ffffffff81135845
#9 shrink_lruvec at ffffffff81135ead
#10 shrink_zone at ffffffff811360c3
#11 shrink_zones at ffffffff81136eff
#12 do_try_to_free_pages at ffffffff8113712f
#13 try_to_free_mem_cgroup_pages at ffffffff811372be
#14 try_charge at ffffffff81189423
#15 mem_cgroup_try_charge at ffffffff8118c6f5
#16 __add_to_page_cache_locked at ffffffff8112137d
#17 add_to_page_cache_lru at ffffffff81121618
#18 pagecache_get_page at ffffffff8112170b
#19 grow_dev_page at ffffffff811c8297
#20 __getblk_slow at ffffffff811c91d6
#21 __getblk_gfp at ffffffff811c92c1
#22 ext4_ext_grow_indepth at ffffffff8124565c
#23 ext4_ext_create_new_leaf at ffffffff81246ca8
#24 ext4_ext_insert_extent at ffffffff81246f09
#25 ext4_ext_map_blocks at ffffffff8124a848
#26 ext4_map_blocks at ffffffff8121a5b7
#27 mpage_map_one_extent at ffffffff8121b1fa
#28 mpage_map_and_submit_extent at ffffffff8121f07b
#29 ext4_writepages at ffffffff8121f6d5
#30 do_writepages at ffffffff8112c490
#31 __filemap_fdatawrite_range at ffffffff81120199
#32 filemap_flush at ffffffff8112041c
#33 ext4_alloc_da_blocks at ffffffff81219da1
#34 ext4_rename at ffffffff81229b91
#35 ext4_rename2 at ffffffff81229e32
#36 vfs_rename at ffffffff811a08a5
#37 SYSC_renameat2 at ffffffff811a3ffc
#38 sys_renameat2 at ffffffff811a408e
#39 sys_rename at ffffffff8119e51e
#40 system_call_fastpath at ffffffff815afa89
Dave Chinner has properly pointed out that this is a deadlock in the
reclaim code because ext4 doesn't submit pages which are marked by
PG_writeback right away.
The heuristic was introduced by commit e62e384e9d ("memcg: prevent OOM
with too many dirty pages") and it was applied only when may_enter_fs
was specified. The code has been changed by c3b94f44fc ("memcg:
further prevent OOM with too many dirty pages") which has removed the
__GFP_FS restriction with a reasoning that we do not get into the fs
code. But this is not sufficient apparently because the fs doesn't
necessarily submit pages marked PG_writeback for IO right away.
ext4_bio_write_page calls io_submit_add_bh but that doesn't necessarily
submit the bio. Instead it tries to map more pages into the bio and
mpage_map_one_extent might trigger memcg charge which might end up
waiting on a page which is marked PG_writeback but hasn't been submitted
yet so we would end up waiting for something that never finishes.
Fix this issue by replacing __GFP_IO by may_enter_fs check (for case 2)
before we go to wait on the writeback. The page fault path, which is
the only path that triggers memcg oom killer since 3.12, shouldn't
require GFP_NOFS and so we shouldn't reintroduce the premature OOM
killer issue which was originally addressed by the heuristic.
As per David Chinner the xfs is doing similar thing since 2.6.15 already
so ext4 is not the only affected filesystem. Moreover he notes:
: For example: IO completion might require unwritten extent conversion
: which executes filesystem transactions and GFP_NOFS allocations. The
: writeback flag on the pages can not be cleared until unwritten
: extent conversion completes. Hence memory reclaim cannot wait on
: page writeback to complete in GFP_NOFS context because it is not
: safe to do so, memcg reclaim or otherwise.
Cc: stable@vger.kernel.org # 3.9+
[tytso@mit.edu: corrected the control flow]
Fixes: c3b94f44fc ("memcg: further prevent OOM with too many dirty pages")
Reported-by: Nikolay Borisov <kernel@kyup.com>
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull cgroup writeback support from Jens Axboe:
"This is the big pull request for adding cgroup writeback support.
This code has been in development for a long time, and it has been
simmering in for-next for a good chunk of this cycle too. This is one
of those problems that has been talked about for at least half a
decade, finally there's a solution and code to go with it.
Also see last weeks writeup on LWN:
http://lwn.net/Articles/648292/"
* 'for-4.2/writeback' of git://git.kernel.dk/linux-block: (85 commits)
writeback, blkio: add documentation for cgroup writeback support
vfs, writeback: replace FS_CGROUP_WRITEBACK with SB_I_CGROUPWB
writeback: do foreign inode detection iff cgroup writeback is enabled
v9fs: fix error handling in v9fs_session_init()
bdi: fix wrong error return value in cgwb_create()
buffer: remove unusued 'ret' variable
writeback: disassociate inodes from dying bdi_writebacks
writeback: implement foreign cgroup inode bdi_writeback switching
writeback: add lockdep annotation to inode_to_wb()
writeback: use unlocked_inode_to_wb transaction in inode_congested()
writeback: implement unlocked_inode_to_wb transaction and use it for stat updates
writeback: implement [locked_]inode_to_wb_and_lock_list()
writeback: implement foreign cgroup inode detection
writeback: make writeback_control track the inode being written back
writeback: relocate wb[_try]_get(), wb_put(), inode_{attach|detach}_wb()
mm: vmscan: disable memcg direct reclaim stalling if cgroup writeback support is in use
writeback: implement memcg writeback domain based throttling
writeback: reset wb_domain->dirty_limit[_tstmp] when memcg domain size changes
writeback: implement memcg wb_domain
writeback: update wb_over_bg_thresh() to use wb_domain aware operations
...
The name SWAP implies that we are dealing with anonymous pages only. In
fact, the original patch that introduced the min_unmapped_ratio logic
was to fix an issue related to file pages. Rename it to RECLAIM_UNMAP
to match what does.
Historically, commit a6dc60f897 ("vmscan: rename sc.may_swap to
may_unmap") renamed .may_swap to .may_unmap, leaving RECLAIM_SWAP
behind. commit 2e2e425989 ("vmscan,memcg: reintroduce sc->may_swap")
reintroduced .may_swap for memory controller.
Signed-off-by: Zhihui Zhang <zzhsuny@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Rik van Riel <riel@redhat.com>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Based upon 675becce15 ("mm: vmscan: do not throttle based on pfmemalloc
reserves if node has no ZONE_NORMAL") from Mel.
We have a system with the following topology:
# numactl -H
available: 3 nodes (0,2-3)
node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31
node 0 size: 28273 MB
node 0 free: 27323 MB
node 2 cpus:
node 2 size: 16384 MB
node 2 free: 0 MB
node 3 cpus: 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47
node 3 size: 30533 MB
node 3 free: 13273 MB
node distances:
node 0 2 3
0: 10 20 20
2: 20 10 20
3: 20 20 10
Node 2 has no free memory, because:
# cat /sys/devices/system/node/node2/hugepages/hugepages-16777216kB/nr_hugepages
1
This leads to the following zoneinfo:
Node 2, zone DMA
pages free 0
min 1840
low 2300
high 2760
scanned 0
spanned 262144
present 262144
managed 262144
...
all_unreclaimable: 1
If one then attempts to allocate some normal 16M hugepages via
echo 37 > /proc/sys/vm/nr_hugepages
The echo never returns and kswapd2 consumes CPU cycles.
This is because throttle_direct_reclaim ends up calling
wait_event(pfmemalloc_wait, pfmemalloc_watermark_ok...).
pfmemalloc_watermark_ok() in turn checks all zones on the node if there
are any reserves, and if so, then indicates the watermarks are ok, by
seeing if there are sufficient free pages.
675becce15 added a condition already for memoryless nodes. In this case,
though, the node has memory, it is just all consumed (and not
reclaimable). Effectively, though, the result is the same on this call to
pfmemalloc_watermark_ok() and thus seems like a reasonable additional
condition.
With this change, the afore-mentioned 16M hugepage allocation attempt
succeeds and correctly round-robins between Nodes 1 and 3.
Signed-off-by: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Anton Blanchard <anton@samba.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Rik van Riel <riel@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Because writeback wasn't cgroup aware before, the usual dirty
throttling mechanism in balance_dirty_pages() didn't work for
processes under memcg limit. The writeback path didn't know how much
memory is available or how fast the dirty pages are being written out
for a given memcg and balance_dirty_pages() didn't have any measure of
IO back pressure for the memcg.
To work around the issue, memcg implemented an ad-hoc dirty throttling
mechanism in the direct reclaim path by stalling on pages under
writeback which are encountered during direct reclaim scan. This is
rather ugly and crude - none of the configurability, fairness, or
bandwidth-proportional distribution of the normal path.
The previous patches implemented proper memcg aware dirty throttling
when cgroup writeback is in use making the ad-hoc mechanism
unnecessary. This patch disables direct reclaim stalling for such
case.
Note: I disabled the parts which seemed obvious and it behaves fine
while testing but my understanding of this code path is
rudimentary and it's quite possible that I got something wrong.
Please let me know if I got some wrong or more global_reclaim()
sites should be updated.
v2: The original patch removed the direct stalling mechanism which
breaks legacy hierarchies. Conditionalize instead of removing.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
In several places, bdi_congested() and its wrappers are used to
determine whether more IOs should be issued. With cgroup writeback
support, this question can't be answered solely based on the bdi
(backing_dev_info). It's dependent on whether the filesystem and bdi
support cgroup writeback and the blkcg the inode is associated with.
This patch implements inode_congested() and its wrappers which take
@inode and determines the congestion state considering cgroup
writeback. The new functions replace bdi_*congested() calls in places
where the query is about specific inode and task.
There are several filesystem users which also fit this criteria but
they should be updated when each filesystem implements cgroup
writeback support.
v2: Now that a given inode is associated with only one wb, congestion
state can be determined independent from the asking task. Drop
@task. Spotted by Vivek. Also, converted to take @inode instead
of @mapping and renamed to inode_congested().
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
When modifying PG_Dirty on cached file pages, update the new
MEM_CGROUP_STAT_DIRTY counter. This is done in the same places where
global NR_FILE_DIRTY is managed. The new memcg stat is visible in the
per memcg memory.stat cgroupfs file. The most recent past attempt at
this was http://thread.gmane.org/gmane.linux.kernel.cgroups/8632
The new accounting supports future efforts to add per cgroup dirty
page throttling and writeback. It also helps an administrator break
down a container's memory usage and provides evidence to understand
memcg oom kills (the new dirty count is included in memcg oom kill
messages).
The ability to move page accounting between memcg
(memory.move_charge_at_immigrate) makes this accounting more
complicated than the global counter. The existing
mem_cgroup_{begin,end}_page_stat() lock is used to serialize move
accounting with stat updates.
Typical update operation:
memcg = mem_cgroup_begin_page_stat(page)
if (TestSetPageDirty()) {
[...]
mem_cgroup_update_page_stat(memcg)
}
mem_cgroup_end_page_stat(memcg)
Summary of mem_cgroup_end_page_stat() overhead:
- Without CONFIG_MEMCG it's a no-op
- With CONFIG_MEMCG and no inter memcg task movement, it's just
rcu_read_lock()
- With CONFIG_MEMCG and inter memcg task movement, it's
rcu_read_lock() + spin_lock_irqsave()
A memcg parameter is added to several routines because their callers
now grab mem_cgroup_begin_page_stat() which returns the memcg later
needed by for mem_cgroup_update_page_stat().
Because mem_cgroup_begin_page_stat() may disable interrupts, some
adjustments are needed:
- move __mark_inode_dirty() from __set_page_dirty() to its caller.
__mark_inode_dirty() locking does not want interrupts disabled.
- use spin_lock_irqsave(tree_lock) rather than spin_lock_irq() in
__delete_from_page_cache(), replace_page_cache_page(),
invalidate_complete_page2(), and __remove_mapping().
text data bss dec hex filename
8925147 1774832 1785856 12485835 be84cb vmlinux-!CONFIG_MEMCG-before
8925339 1774832 1785856 12486027 be858b vmlinux-!CONFIG_MEMCG-after
+192 text bytes
8965977 1784992 1785856 12536825 bf4bf9 vmlinux-CONFIG_MEMCG-before
8966750 1784992 1785856 12537598 bf4efe vmlinux-CONFIG_MEMCG-after
+773 text bytes
Performance tests run on v4.0-rc1-36-g4f671fe2f952. Lower is better for
all metrics, they're all wall clock or cycle counts. The read and write
fault benchmarks just measure fault time, they do not include I/O time.
* CONFIG_MEMCG not set:
baseline patched
kbuild 1m25.030000(+-0.088% 3 samples) 1m25.426667(+-0.120% 3 samples)
dd write 100 MiB 0.859211561 +-15.10% 0.874162885 +-15.03%
dd write 200 MiB 1.670653105 +-17.87% 1.669384764 +-11.99%
dd write 1000 MiB 8.434691190 +-14.15% 8.474733215 +-14.77%
read fault cycles 254.0(+-0.000% 10 samples) 253.0(+-0.000% 10 samples)
write fault cycles 2021.2(+-3.070% 10 samples) 1984.5(+-1.036% 10 samples)
* CONFIG_MEMCG=y root_memcg:
baseline patched
kbuild 1m25.716667(+-0.105% 3 samples) 1m25.686667(+-0.153% 3 samples)
dd write 100 MiB 0.855650830 +-14.90% 0.887557919 +-14.90%
dd write 200 MiB 1.688322953 +-12.72% 1.667682724 +-13.33%
dd write 1000 MiB 8.418601605 +-14.30% 8.673532299 +-15.00%
read fault cycles 266.0(+-0.000% 10 samples) 266.0(+-0.000% 10 samples)
write fault cycles 2051.7(+-1.349% 10 samples) 2049.6(+-1.686% 10 samples)
* CONFIG_MEMCG=y non-root_memcg:
baseline patched
kbuild 1m26.120000(+-0.273% 3 samples) 1m25.763333(+-0.127% 3 samples)
dd write 100 MiB 0.861723964 +-15.25% 0.818129350 +-14.82%
dd write 200 MiB 1.669887569 +-13.30% 1.698645885 +-13.27%
dd write 1000 MiB 8.383191730 +-14.65% 8.351742280 +-14.52%
read fault cycles 265.7(+-0.172% 10 samples) 267.0(+-0.000% 10 samples)
write fault cycles 2070.6(+-1.512% 10 samples) 2084.4(+-2.148% 10 samples)
As expected anon page faults are not affected by this patch.
tj: Updated to apply on top of the recent cancel_dirty_page() changes.
Signed-off-by: Sha Zhengju <handai.szj@gmail.com>
Signed-off-by: Greg Thelen <gthelen@google.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@fb.com>
Merge third set of updates from Andrew Morton:
- the rest of MM
[ This includes getting rid of the numa hinting bits, in favor of
just generic protnone logic. Yay. - Linus ]
- core kernel
- procfs
- some of lib/ (lots of lib/ material this time)
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (104 commits)
lib/lcm.c: replace include
lib/percpu_ida.c: remove redundant includes
lib/strncpy_from_user.c: replace module.h include
lib/stmp_device.c: replace module.h include
lib/sort.c: move include inside #if 0
lib/show_mem.c: remove redundant include
lib/radix-tree.c: change to simpler include
lib/plist.c: remove redundant include
lib/nlattr.c: remove redundant include
lib/kobject_uevent.c: remove redundant include
lib/llist.c: remove redundant include
lib/md5.c: simplify include
lib/list_sort.c: rearrange includes
lib/genalloc.c: remove redundant include
lib/idr.c: remove redundant include
lib/halfmd4.c: simplify includes
lib/dynamic_queue_limits.c: simplify includes
lib/sort.c: use simpler includes
lib/interval_tree.c: simplify includes
hexdump: make it return number of bytes placed in buffer
...
This patch adds SHRINKER_MEMCG_AWARE flag. If a shrinker has this flag
set, it will be called per memory cgroup. The memory cgroup to scan
objects from is passed in shrink_control->memcg. If the memory cgroup
is NULL, a memcg aware shrinker is supposed to scan objects from the
global list. Unaware shrinkers are only called on global pressure with
memcg=NULL.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Greg Thelen <gthelen@google.com>
Cc: Glauber Costa <glommer@gmail.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull backing device changes from Jens Axboe:
"This contains a cleanup of how the backing device is handled, in
preparation for a rework of the life time rules. In this part, the
most important change is to split the unrelated nommu mmap flags from
it, but also removing a backing_dev_info pointer from the
address_space (and inode), and a cleanup of other various minor bits.
Christoph did all the work here, I just fixed an oops with pages that
have a swap backing. Arnd fixed a missing export, and Oleg killed the
lustre backing_dev_info from staging. Last patch was from Al,
unexporting parts that are now no longer needed outside"
* 'for-3.20/bdi' of git://git.kernel.dk/linux-block:
Make super_blocks and sb_lock static
mtd: export new mtd_mmap_capabilities
fs: make inode_to_bdi() handle NULL inode
staging/lustre/llite: get rid of backing_dev_info
fs: remove default_backing_dev_info
fs: don't reassign dirty inodes to default_backing_dev_info
nfs: don't call bdi_unregister
ceph: remove call to bdi_unregister
fs: remove mapping->backing_dev_info
fs: export inode_to_bdi and use it in favor of mapping->backing_dev_info
nilfs2: set up s_bdi like the generic mount_bdev code
block_dev: get bdev inode bdi directly from the block device
block_dev: only write bdev inode on close
fs: introduce f_op->mmap_capabilities for nommu mmap support
fs: kill BDI_CAP_SWAP_BACKED
fs: deduplicate noop_backing_dev_info
Introduce the basic control files to account, partition, and limit
memory using cgroups in default hierarchy mode.
This interface versioning allows us to address fundamental design
issues in the existing memory cgroup interface, further explained
below. The old interface will be maintained indefinitely, but a
clearer model and improved workload performance should encourage
existing users to switch over to the new one eventually.
The control files are thus:
- memory.current shows the current consumption of the cgroup and its
descendants, in bytes.
- memory.low configures the lower end of the cgroup's expected
memory consumption range. The kernel considers memory below that
boundary to be a reserve - the minimum that the workload needs in
order to make forward progress - and generally avoids reclaiming
it, unless there is an imminent risk of entering an OOM situation.
- memory.high configures the upper end of the cgroup's expected
memory consumption range. A cgroup whose consumption grows beyond
this threshold is forced into direct reclaim, to work off the
excess and to throttle new allocations heavily, but is generally
allowed to continue and the OOM killer is not invoked.
- memory.max configures the hard maximum amount of memory that the
cgroup is allowed to consume before the OOM killer is invoked.
- memory.events shows event counters that indicate how often the
cgroup was reclaimed while below memory.low, how often it was
forced to reclaim excess beyond memory.high, how often it hit
memory.max, and how often it entered OOM due to memory.max. This
allows users to identify configuration problems when observing a
degradation in workload performance. An overcommitted system will
have an increased rate of low boundary breaches, whereas increased
rates of high limit breaches, maximum hits, or even OOM situations
will indicate internally overcommitted cgroups.
For existing users of memory cgroups, the following deviations from
the current interface are worth pointing out and explaining:
- The original lower boundary, the soft limit, is defined as a limit
that is per default unset. As a result, the set of cgroups that
global reclaim prefers is opt-in, rather than opt-out. The costs
for optimizing these mostly negative lookups are so high that the
implementation, despite its enormous size, does not even provide
the basic desirable behavior. First off, the soft limit has no
hierarchical meaning. All configured groups are organized in a
global rbtree and treated like equal peers, regardless where they
are located in the hierarchy. This makes subtree delegation
impossible. Second, the soft limit reclaim pass is so aggressive
that it not just introduces high allocation latencies into the
system, but also impacts system performance due to overreclaim, to
the point where the feature becomes self-defeating.
The memory.low boundary on the other hand is a top-down allocated
reserve. A cgroup enjoys reclaim protection when it and all its
ancestors are below their low boundaries, which makes delegation
of subtrees possible. Secondly, new cgroups have no reserve per
default and in the common case most cgroups are eligible for the
preferred reclaim pass. This allows the new low boundary to be
efficiently implemented with just a minor addition to the generic
reclaim code, without the need for out-of-band data structures and
reclaim passes. Because the generic reclaim code considers all
cgroups except for the ones running low in the preferred first
reclaim pass, overreclaim of individual groups is eliminated as
well, resulting in much better overall workload performance.
- The original high boundary, the hard limit, is defined as a strict
limit that can not budge, even if the OOM killer has to be called.
But this generally goes against the goal of making the most out of
the available memory. The memory consumption of workloads varies
during runtime, and that requires users to overcommit. But doing
that with a strict upper limit requires either a fairly accurate
prediction of the working set size or adding slack to the limit.
Since working set size estimation is hard and error prone, and
getting it wrong results in OOM kills, most users tend to err on
the side of a looser limit and end up wasting precious resources.
The memory.high boundary on the other hand can be set much more
conservatively. When hit, it throttles allocations by forcing
them into direct reclaim to work off the excess, but it never
invokes the OOM killer. As a result, a high boundary that is
chosen too aggressively will not terminate the processes, but
instead it will lead to gradual performance degradation. The user
can monitor this and make corrections until the minimal memory
footprint that still gives acceptable performance is found.
In extreme cases, with many concurrent allocations and a complete
breakdown of reclaim progress within the group, the high boundary
can be exceeded. But even then it's mostly better to satisfy the
allocation from the slack available in other groups or the rest of
the system than killing the group. Otherwise, memory.max is there
to limit this type of spillover and ultimately contain buggy or
even malicious applications.
- The original control file names are unwieldy and inconsistent in
many different ways. For example, the upper boundary hit count is
exported in the memory.failcnt file, but an OOM event count has to
be manually counted by listening to memory.oom_control events, and
lower boundary / soft limit events have to be counted by first
setting a threshold for that value and then counting those events.
Also, usage and limit files encode their units in the filename.
That makes the filenames very long, even though this is not
information that a user needs to be reminded of every time they
type out those names.
To address these naming issues, as well as to signal clearly that
the new interface carries a new configuration model, the naming
conventions in it necessarily differ from the old interface.
- The original limit files indicate the state of an unset limit with
a very high number, and a configured limit can be unset by echoing
-1 into those files. But that very high number is implementation
and architecture dependent and not very descriptive. And while -1
can be understood as an underflow into the highest possible value,
-2 or -10M etc. do not work, so it's not inconsistent.
memory.low, memory.high, and memory.max will use the string
"infinity" to indicate and set the highest possible value.
[akpm@linux-foundation.org: use seq_puts() for basic strings]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Cc: Greg Thelen <gthelen@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since commit b2052564e6 ("mm: memcontrol: continue cache reclaim from
offlined groups") pages charged to a memory cgroup are not reparented when
the cgroup is removed. Instead, they are supposed to be reclaimed in a
regular way, along with pages accounted to online memory cgroups.
However, an lruvec of an offline memory cgroup will sooner or later get so
small that it will be scanned only at low scan priorities (see
get_scan_count()). Therefore, if there are enough reclaimable pages in
big lruvecs, pages accounted to offline memory cgroups will never be
scanned at all, wasting memory.
Fix this by unconditionally forcing scanning dead lruvecs from kswapd.
[akpm@linux-foundation.org: fix build]
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Kswapd in balance_pgdate() currently uses wake_up() on processes waiting
in throttle_direct_reclaim(), which only wakes up a single process. This
might leave processes waiting for longer than necessary, until the check
is reached in the next loop iteration. Processes might also be left
waiting if zone was fully balanced in single iteration. Note that the
comment in balance_pgdat() also says "Wake them", so waking up a single
process does not seem intentional.
Thus, replace wake_up() with wake_up_all().
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Now that we got rid of the bdi abuse on character devices we can always use
sb->s_bdi to get at the backing_dev_info for a file, except for the block
device special case. Export inode_to_bdi and replace uses of
mapping->backing_dev_info with it to prepare for the removal of
mapping->backing_dev_info.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>
Charles Shirron and Paul Cassella from Cray Inc have reported kswapd
stuck in a busy loop with nothing left to balance, but
kswapd_try_to_sleep() failing to sleep. Their analysis found the cause
to be a combination of several factors:
1. A process is waiting in throttle_direct_reclaim() on pgdat->pfmemalloc_wait
2. The process has been killed (by OOM in this case), but has not yet been
scheduled to remove itself from the waitqueue and die.
3. kswapd checks for throttled processes in prepare_kswapd_sleep():
if (waitqueue_active(&pgdat->pfmemalloc_wait)) {
wake_up(&pgdat->pfmemalloc_wait);
return false; // kswapd will not go to sleep
}
However, for a process that was already killed, wake_up() does not remove
the process from the waitqueue, since try_to_wake_up() checks its state
first and returns false when the process is no longer waiting.
4. kswapd is running on the same CPU as the only CPU that the process is
allowed to run on (through cpus_allowed, or possibly single-cpu system).
5. CONFIG_PREEMPT_NONE=y kernel is used. If there's nothing to balance, kswapd
encounters no voluntary preemption points and repeatedly fails
prepare_kswapd_sleep(), blocking the process from running and removing
itself from the waitqueue, which would let kswapd sleep.
So, the source of the problem is that we prevent kswapd from going to
sleep until there are processes waiting on the pfmemalloc_wait queue,
and a process waiting on a queue is guaranteed to be removed from the
queue only when it gets scheduled. This was done to make sure that no
process is left sleeping on pfmemalloc_wait when kswapd itself goes to
sleep.
However, it isn't necessary to postpone kswapd sleep until the
pfmemalloc_wait queue actually empties. To prevent processes from being
left sleeping, it's actually enough to guarantee that all processes
waiting on pfmemalloc_wait queue have been woken up by the time we put
kswapd to sleep.
This patch therefore fixes this issue by substituting 'wake_up' with
'wake_up_all' and removing 'return false' in the code snippet from
prepare_kswapd_sleep() above. Note that if any process puts itself in
the queue after this waitqueue_active() check, or after the wake up
itself, it means that the process will also wake up kswapd - and since
we are under prepare_to_wait(), the wake up won't be missed. Also we
update the comment prepare_kswapd_sleep() to hopefully more clearly
describe the races it is preventing.
Fixes: 5515061d22 ("mm: throttle direct reclaimers if PF_MEMALLOC reserves are low and swap is backed by network storage")
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: <stable@vger.kernel.org> [3.6+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The slab shrinkers are currently invoked from the zonelist walkers in
kswapd, direct reclaim, and zone reclaim, all of which roughly gauge the
eligible LRU pages and assemble a nodemask to pass to NUMA-aware
shrinkers, which then again have to walk over the nodemask. This is
redundant code, extra runtime work, and fairly inaccurate when it comes to
the estimation of actually scannable LRU pages. The code duplication will
only get worse when making the shrinkers cgroup-aware and requiring them
to have out-of-band cgroup hierarchy walks as well.
Instead, invoke the shrinkers from shrink_zone(), which is where all
reclaimers end up, to avoid this duplication.
Take the count for eligible LRU pages out of get_scan_count(), which
considers many more factors than just the availability of swap space, like
zone_reclaimable_pages() currently does. Accumulate the number over all
visited lruvecs to get the per-zone value.
Some nodes have multiple zones due to memory addressing restrictions. To
avoid putting too much pressure on the shrinkers, only invoke them once
for each such node, using the class zone of the allocation as the pivot
zone.
For now, this integrates the slab shrinking better into the reclaim logic
and gets rid of duplicative invocations from kswapd, direct reclaim, and
zone reclaim. It also prepares for cgroup-awareness, allowing
memcg-capable shrinkers to be added at the lruvec level without much
duplication of both code and runtime work.
This changes kswapd behavior, which used to invoke the shrinkers for each
zone, but with scan ratios gathered from the entire node, resulting in
meaningless pressure quantities on multi-zone nodes.
Zone reclaim behavior also changes. It used to shrink slabs until the
same amount of pages were shrunk as were reclaimed from the LRUs. Now it
merely invokes the shrinkers once with the zone's scan ratio, which makes
the shrinkers go easier on caches that implement aging and would prefer
feeding back pressure from recently used slab objects to unused LRU pages.
[vdavydov@parallels.com: assure class zone is populated]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull cgroup update from Tejun Heo:
"cpuset got simplified a bit. cgroup core got a fix on unified
hierarchy and grew some effective css related interfaces which will be
used for blkio support for writeback IO traffic which is currently
being worked on"
* 'for-3.19' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup: implement cgroup_get_e_css()
cgroup: add cgroup_subsys->css_e_css_changed()
cgroup: add cgroup_subsys->css_released()
cgroup: fix the async css offline wait logic in cgroup_subtree_control_write()
cgroup: restructure child_subsys_mask handling in cgroup_subtree_control_write()
cgroup: separate out cgroup_calc_child_subsys_mask() from cgroup_refresh_child_subsys_mask()
cpuset: lock vs unlock typo
cpuset: simplify cpuset_node_allowed API
cpuset: convert callback_mutex to a spinlock
Compaction relies on zone watermark checks for decisions such as if it's
worth to start compacting in compaction_suitable() or whether compaction
should stop in compact_finished(). The watermark checks take
classzone_idx and alloc_flags parameters, which are related to the memory
allocation request. But from the context of compaction they are currently
passed as 0, including the direct compaction which is invoked to satisfy
the allocation request, and could therefore know the proper values.
The lack of proper values can lead to mismatch between decisions taken
during compaction and decisions related to the allocation request. Lack
of proper classzone_idx value means that lowmem_reserve is not taken into
account. This has manifested (during recent changes to deferred
compaction) when DMA zone was used as fallback for preferred Normal zone.
compaction_suitable() without proper classzone_idx would think that the
watermarks are already satisfied, but watermark check in
get_page_from_freelist() would fail. Because of this problem, deferring
compaction has extra complexity that can be removed in the following
patch.
The issue (not confirmed in practice) with missing alloc_flags is opposite
in nature. For allocations that include ALLOC_HIGH, ALLOC_HIGHER or
ALLOC_CMA in alloc_flags (the last includes all MOVABLE allocations on
CMA-enabled systems) the watermark checking in compaction with 0 passed
will be stricter than in get_page_from_freelist(). In these cases
compaction might be running for a longer time than is really needed.
Another issue compaction_suitable() is that the check for "does the zone
need compaction at all?" comes only after the check "does the zone have
enough free free pages to succeed compaction". The latter considers extra
pages for migration and can therefore in some situations fail and return
COMPACT_SKIPPED, although the high-order allocation would succeed and we
should return COMPACT_PARTIAL.
This patch fixes these problems by adding alloc_flags and classzone_idx to
struct compact_control and related functions involved in direct compaction
and watermark checking. Where possible, all other callers of
compaction_suitable() pass proper values where those are known. This is
currently limited to classzone_idx, which is sometimes known in kswapd
context. However, the direct reclaim callers should_continue_reclaim()
and compaction_ready() do not currently know the proper values, so the
coordination between reclaim and compaction may still not be as accurate
as it could. This can be fixed later, if it's shown to be an issue.
Additionaly the checks in compact_suitable() are reordered to address the
second issue described above.
The effect of this patch should be slightly better high-order allocation
success rates and/or less compaction overhead, depending on the type of
allocations and presence of CMA. It allows simplifying deferred
compaction code in a followup patch.
When testing with stress-highalloc, there was some slight improvement
(which might be just due to variance) in success rates of non-THP-like
allocations.
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Christoph Lameter <cl@linux.com>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
shrink_page_list() counts all pages with a mapping, including clean pages,
toward nr_congested if they're on a write-congested BDI.
shrink_inactive_list() then sets ZONE_CONGESTED if nr_dirty ==
nr_congested. Fix this apples-to-oranges comparison by only counting
pages for nr_congested if they count for nr_dirty.
Signed-off-by: Jamie Liu <jamieliu@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Greg Thelen <gthelen@google.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch replaces printk(KERN_ERR..) with pr_err found under
shrink_slab. Thus it also reduces one line extra because of formatting.
Signed-off-by: Pintu Kumar <pintu.k@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Current cpuset API for checking if a zone/node is allowed to allocate
from looks rather awkward. We have hardwall and softwall versions of
cpuset_node_allowed with the softwall version doing literally the same
as the hardwall version if __GFP_HARDWALL is passed to it in gfp flags.
If it isn't, the softwall version may check the given node against the
enclosing hardwall cpuset, which it needs to take the callback lock to
do.
Such a distinction was introduced by commit 02a0e53d82 ("cpuset:
rework cpuset_zone_allowed api"). Before, we had the only version with
the __GFP_HARDWALL flag determining its behavior. The purpose of the
commit was to avoid sleep-in-atomic bugs when someone would mistakenly
call the function without the __GFP_HARDWALL flag for an atomic
allocation. The suffixes introduced were intended to make the callers
think before using the function.
However, since the callback lock was converted from mutex to spinlock by
the previous patch, the softwall check function cannot sleep, and these
precautions are no longer necessary.
So let's simplify the API back to the single check.
Suggested-by: David Rientjes <rientjes@google.com>
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: Zefan Li <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
In a memcg with even just moderate cache pressure, success rates for
transparent huge page allocations drop to zero, wasting a lot of effort
that the allocator puts into assembling these pages.
The reason for this is that the memcg reclaim code was never designed for
higher-order charges. It reclaims in small batches until there is room
for at least one page. Huge page charges only succeed when these batches
add up over a series of huge faults, which is unlikely under any
significant load involving order-0 allocations in the group.
Remove that loop on the memcg side in favor of passing the actual reclaim
goal to direct reclaim, which is already set up and optimized to meet
higher-order goals efficiently.
This brings memcg's THP policy in line with the system policy: if the
allocator painstakingly assembles a hugepage, memcg will at least make an
honest effort to charge it. As a result, transparent hugepage allocation
rates amid cache activity are drastically improved:
vanilla patched
pgalloc 4717530.80 ( +0.00%) 4451376.40 ( -5.64%)
pgfault 491370.60 ( +0.00%) 225477.40 ( -54.11%)
pgmajfault 2.00 ( +0.00%) 1.80 ( -6.67%)
thp_fault_alloc 0.00 ( +0.00%) 531.60 (+100.00%)
thp_fault_fallback 749.00 ( +0.00%) 217.40 ( -70.88%)
[ Note: this may in turn increase memory consumption from internal
fragmentation, which is an inherent risk of transparent hugepages.
Some setups may have to adjust the memcg limits accordingly to
accomodate this - or, if the machine is already packed to capacity,
disable the transparent huge page feature. ]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Dave Hansen <dave@sr71.net>
Cc: Greg Thelen <gthelen@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Page reclaim tests zone_is_reclaim_dirty(), but the site that actually
sets this state does zone_set_flag(zone, ZONE_TAIL_LRU_DIRTY), sending the
reader through layers indirection just to track down a simple bit.
Remove all zone flag wrappers and just use bitops against zone->flags
directly. It's just as readable and the lines are barely any longer.
Also rename ZONE_TAIL_LRU_DIRTY to ZONE_DIRTY to match ZONE_WRITEBACK, and
remove the zone_flags_t typedef.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The deprecation warnings for the scan_unevictable interface triggers by
scripts doing `sysctl -a | grep something else'. This is annoying and not
helpful.
The interface has been defunct since 264e56d824 ("mm: disable user
interface to manually rescue unevictable pages"), which was in 2011, and
there haven't been any reports of usecases for it, only reports that the
deprecation warnings are annying. It's unlikely that anybody is using
this interface specifically at this point, so remove it.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When direct sync compaction is often unsuccessful, it may become deferred
for some time to avoid further useless attempts, both sync and async.
Successful high-order allocations un-defer compaction, while further
unsuccessful compaction attempts prolong the compaction deferred period.
Currently the checking and setting deferred status is performed only on
the preferred zone of the allocation that invoked direct compaction. But
compaction itself is attempted on all eligible zones in the zonelist, so
the behavior is suboptimal and may lead both to scenarios where 1)
compaction is attempted uselessly, or 2) where it's not attempted despite
good chances of succeeding, as shown on the examples below:
1) A direct compaction with Normal preferred zone failed and set
deferred compaction for the Normal zone. Another unrelated direct
compaction with DMA32 as preferred zone will attempt to compact DMA32
zone even though the first compaction attempt also included DMA32 zone.
In another scenario, compaction with Normal preferred zone failed to
compact Normal zone, but succeeded in the DMA32 zone, so it will not
defer compaction. In the next attempt, it will try Normal zone which
will fail again, instead of skipping Normal zone and trying DMA32
directly.
2) Kswapd will balance DMA32 zone and reset defer status based on
watermarks looking good. A direct compaction with preferred Normal
zone will skip compaction of all zones including DMA32 because Normal
was still deferred. The allocation might have succeeded in DMA32, but
won't.
This patch makes compaction deferring work on individual zone basis
instead of preferred zone. For each zone, it checks compaction_deferred()
to decide if the zone should be skipped. If watermarks fail after
compacting the zone, defer_compaction() is called. The zone where
watermarks passed can still be deferred when the allocation attempt is
unsuccessful. When allocation is successful, compaction_defer_reset() is
called for the zone containing the allocated page. This approach should
approximate calling defer_compaction() only on zones where compaction was
attempted and did not yield allocated page. There might be corner cases
but that is inevitable as long as the decision to stop compacting dues not
guarantee that a page will be allocated.
Due to a new COMPACT_DEFERRED return value, some functions relying
implicitly on COMPACT_SKIPPED = 0 had to be updated, with comments made
more accurate. The did_some_progress output parameter of
__alloc_pages_direct_compact() is removed completely, as the caller
actually does not use it after compaction sets it - it is only considered
when direct reclaim sets it.
During testing on a two-node machine with a single very small Normal zone
on node 1, this patch has improved success rates in stress-highalloc
mmtests benchmark. The success here were previously made worse by commit
3a025760fc ("mm: page_alloc: spill to remote nodes before waking
kswapd") as kswapd was no longer resetting often enough the deferred
compaction for the Normal zone, and DMA32 zones on both nodes were thus
not considered for compaction. On different machine, success rates were
improved with __GFP_NO_KSWAPD allocations.
[akpm@linux-foundation.org: fix CONFIG_COMPACTION=n build]
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pages are now uncharged at release time, and all sources of batched
uncharges operate on lists of pages. Directly use those lists, and
get rid of the per-task batching state.
This also batches statistics accounting, in addition to the res
counter charges, to reduce IRQ-disabling and re-enabling.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The memcg uncharging code that is involved towards the end of a page's
lifetime - truncation, reclaim, swapout, migration - is impressively
complicated and fragile.
Because anonymous and file pages were always charged before they had their
page->mapping established, uncharges had to happen when the page type
could still be known from the context; as in unmap for anonymous, page
cache removal for file and shmem pages, and swap cache truncation for swap
pages. However, these operations happen well before the page is actually
freed, and so a lot of synchronization is necessary:
- Charging, uncharging, page migration, and charge migration all need
to take a per-page bit spinlock as they could race with uncharging.
- Swap cache truncation happens during both swap-in and swap-out, and
possibly repeatedly before the page is actually freed. This means
that the memcg swapout code is called from many contexts that make
no sense and it has to figure out the direction from page state to
make sure memory and memory+swap are always correctly charged.
- On page migration, the old page might be unmapped but then reused,
so memcg code has to prevent untimely uncharging in that case.
Because this code - which should be a simple charge transfer - is so
special-cased, it is not reusable for replace_page_cache().
But now that charged pages always have a page->mapping, introduce
mem_cgroup_uncharge(), which is called after the final put_page(), when we
know for sure that nobody is looking at the page anymore.
For page migration, introduce mem_cgroup_migrate(), which is called after
the migration is successful and the new page is fully rmapped. Because
the old page is no longer uncharged after migration, prevent double
charges by decoupling the page's memcg association (PCG_USED and
pc->mem_cgroup) from the page holding an actual charge. The new bits
PCG_MEM and PCG_MEMSW represent the respective charges and are transferred
to the new page during migration.
mem_cgroup_migrate() is suitable for replace_page_cache() as well,
which gets rid of mem_cgroup_replace_page_cache(). However, care
needs to be taken because both the source and the target page can
already be charged and on the LRU when fuse is splicing: grab the page
lock on the charge moving side to prevent changing pc->mem_cgroup of a
page under migration. Also, the lruvecs of both pages change as we
uncharge the old and charge the new during migration, and putback may
race with us, so grab the lru lock and isolate the pages iff on LRU to
prevent races and ensure the pages are on the right lruvec afterward.
Swap accounting is massively simplified: because the page is no longer
uncharged as early as swap cache deletion, a new mem_cgroup_swapout() can
transfer the page's memory+swap charge (PCG_MEMSW) to the swap entry
before the final put_page() in page reclaim.
Finally, page_cgroup changes are now protected by whatever protection the
page itself offers: anonymous pages are charged under the page table lock,
whereas page cache insertions, swapin, and migration hold the page lock.
Uncharging happens under full exclusion with no outstanding references.
Charging and uncharging also ensure that the page is off-LRU, which
serializes against charge migration. Remove the very costly page_cgroup
lock and set pc->flags non-atomically.
[mhocko@suse.cz: mem_cgroup_charge_statistics needs preempt_disable]
[vdavydov@parallels.com: fix flags definition]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Tested-by: Jet Chen <jet.chen@intel.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Tested-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When memory cgoups are enabled, the code that decides to force to scan
anonymous pages in get_scan_count() compares global values (free,
high_watermark) to a value that is restricted to a memory cgroup (file).
It make the code over-eager to force anon scan.
For instance, it will force anon scan when scanning a memcg that is
mainly populated by anonymous page, even when there is plenty of file
pages to get rid of in others memcgs, even when swappiness == 0. It
breaks user's expectation about swappiness and hurts performance.
This patch makes sure that forced anon scan only happens when there not
enough file pages for the all zone, not just in one random memcg.
[hannes@cmpxchg.org: cleanups]
Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Quite a while ago, get_scan_ratio() has been renamed get_scan_count(),
however a comment in shrink_active_list() still mention it. This patch
fixes the outdated comment.
Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
zone->pages_scanned is a write-intensive cache line during page reclaim
and it's also updated during page free. Move the counter into vmstat to
take advantage of the per-cpu updates and do not update it in the free
paths unless necessary.
On a small UMA machine running tiobench the difference is marginal. On
a 4-node machine the overhead is more noticable. Note that automatic
NUMA balancing was disabled for this test as otherwise the system CPU
overhead is unpredictable.
3.16.0-rc3 3.16.0-rc3 3.16.0-rc3
vanillarearrange-v5 vmstat-v5
User 746.94 759.78 774.56
System 65336.22 58350.98 32847.27
Elapsed 27553.52 27282.02 27415.04
Note that the overhead reduction will vary depending on where exactly
pages are allocated and freed.
Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
vm_total_pages is calculated by nr_free_pagecache_pages(), which counts
the number of pages which are beyond the high watermark within all
zones. So vm_total_pages is not equal to total number of pages which
the VM controls.
Signed-off-by: Wang Sheng-Hui <shhuiw@gmail.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Swappiness is determined for each scanned memcg individually in
shrink_zone() and is not a parameter that applies throughout the reclaim
scan. Move it out of struct scan_control to prevent accidental use of a
stale value.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Direct reclaim currently calls shrink_zones() to reclaim all members of
a zonelist, and if that wasn't successful it does another pass through
the same zonelist to check overall reclaimability.
Just check reclaimability in shrink_zones() directly and propagate the
result through the return value. Then remove all_unreclaimable().
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Page reclaim for a higher-order page runs until compaction is ready,
then aborts and signals this situation through the return value of
shrink_zones(). This is an oddly specific signal to encode in the
return value of shrink_zones(), though, and can be quite confusing.
Introduce sc->compaction_ready and signal the compactability of the
zones out-of-band to free up the return value of shrink_zones() for
actual zone reclaimability.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Michal Hocko <mhocko@suse.cz>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
shrink_zones() has a special branch to skip the all_unreclaimable()
check during hibernation, because a frozen kswapd can't mark a zone
unreclaimable.
But ever since commit 6e543d5780 ("mm: vmscan: fix
do_try_to_free_pages() livelock"), determining a zone to be
unreclaimable is done by directly looking at its scan history and no
longer relies on kswapd setting the per-zone flag.
Remove this branch and let shrink_zones() check the reclaimability of
the target zones regardless of hibernation state.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: KOSAKI Motohiro <Kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull vfs updates from Al Viro:
"This the bunch that sat in -next + lock_parent() fix. This is the
minimal set; there's more pending stuff.
In particular, I really hope to get acct.c fixes merged this cycle -
we need that to deal sanely with delayed-mntput stuff. In the next
pile, hopefully - that series is fairly short and localized
(kernel/acct.c, fs/super.c and fs/namespace.c). In this pile: more
iov_iter work. Most of prereqs for ->splice_write with sane locking
order are there and Kent's dio rewrite would also fit nicely on top of
this pile"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (70 commits)
lock_parent: don't step on stale ->d_parent of all-but-freed one
kill generic_file_splice_write()
ceph: switch to iter_file_splice_write()
shmem: switch to iter_file_splice_write()
nfs: switch to iter_splice_write_file()
fs/splice.c: remove unneeded exports
ocfs2: switch to iter_file_splice_write()
->splice_write() via ->write_iter()
bio_vec-backed iov_iter
optimize copy_page_{to,from}_iter()
bury generic_file_aio_{read,write}
lustre: get rid of messing with iovecs
ceph: switch to ->write_iter()
ceph_sync_direct_write: stop poking into iov_iter guts
ceph_sync_read: stop poking into iov_iter guts
new helper: copy_page_from_iter()
fuse: switch to ->write_iter()
btrfs: switch to ->write_iter()
ocfs2: switch to ->write_iter()
xfs: switch to ->write_iter()
...
shrink_inactive_list() used to wait 0.1s to avoid congestion when all
the pages that were isolated from the inactive list were dirty but not
under active writeback. That makes no real sense, and apparently causes
major interactivity issues under some loads since 3.11.
The ostensible reason for it was to wait for kswapd to start writing
pages, but that seems questionable as well, since the congestion wait
code seems to trigger for kswapd itself as well. Also, the logic behind
delaying anything when we haven't actually started writeback is not
clear - it only delays actually starting that writeback.
We'll still trigger the congestion waiting if
(a) the process is kswapd, and we hit pages flagged for immediate
reclaim
(b) the process is not kswapd, and the zone backing dev writeback is
actually congested.
This probably needs to be revisited, but as it is this fixes a reported
regression.
Reported-by: Felipe Contreras <felipe.contreras@gmail.com>
Pinpointed-by: Hillf Danton <dhillf@gmail.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
printk is meant to be used with an associated log level. There are some
instances of printk scattered around the mm code where the log level is
missing. Add a log level and adhere to suggestions by
scripts/checkpatch.pl by moving to the pr_* macros.
Also add the typical pr_fmt definition so that print statements can be
easily traced back to the modules where they occur, correlated one with
another, etc. This will require the removal of some (now redundant)
prefixes on a few print statements.
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Memory reclaim always uses swappiness of the reclaim target memcg
(origin of the memory pressure) or vm_swappiness for global memory
reclaim. This behavior was consistent (except for difference between
global and hard limit reclaim) because swappiness was enforced to be
consistent within each memcg hierarchy.
After "mm: memcontrol: remove hierarchy restrictions for swappiness and
oom_control" each memcg can have its own swappiness independent of
hierarchical parents, though, so the consistency guarantee is gone.
This can lead to an unexpected behavior. Say that a group is explicitly
configured to not swapout by memory.swappiness=0 but its memory gets
swapped out anyway when the memory pressure comes from its parent with a
It is also unexpected that the knob is meaningless without setting the
hard limit which would trigger the reclaim and enforce the swappiness.
There are setups where the hard limit is configured higher in the
hierarchy by an administrator and children groups are under control of
somebody else who is interested in the swapout behavior but not
necessarily about the memory limit.
From a semantic point of view swappiness is an attribute defining anon
vs.
file proportional scanning of LRU which is memcg specific (unlike
charges which are propagated up the hierarchy) so it should be applied
to the particular memcg's LRU regardless where the memory pressure comes
from.
This patch removes vmscan_swappiness() and stores the swappiness into
the scan_control structure. mem_cgroup_swappiness is then used to
provide the correct value before shrink_lruvec is called. The global
vm_swappiness is used for the root memcg.
[hughd@google.com: oopses immediately when booted with cgroup_disable=memory]
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When kswapd exits, it can end up taking locks that were previously held
by allocating tasks while they waited for reclaim. Lockdep currently
warns about this:
On Wed, May 28, 2014 at 06:06:34PM +0800, Gu Zheng wrote:
> inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM_FS-R} usage.
> kswapd2/1151 [HC0[0]:SC0[0]:HE1:SE1] takes:
> (&sig->group_rwsem){+++++?}, at: exit_signals+0x24/0x130
> {RECLAIM_FS-ON-W} state was registered at:
> mark_held_locks+0xb9/0x140
> lockdep_trace_alloc+0x7a/0xe0
> kmem_cache_alloc_trace+0x37/0x240
> flex_array_alloc+0x99/0x1a0
> cgroup_attach_task+0x63/0x430
> attach_task_by_pid+0x210/0x280
> cgroup_procs_write+0x16/0x20
> cgroup_file_write+0x120/0x2c0
> vfs_write+0xc0/0x1f0
> SyS_write+0x4c/0xa0
> tracesys+0xdd/0xe2
> irq event stamp: 49
> hardirqs last enabled at (49): _raw_spin_unlock_irqrestore+0x36/0x70
> hardirqs last disabled at (48): _raw_spin_lock_irqsave+0x2b/0xa0
> softirqs last enabled at (0): copy_process.part.24+0x627/0x15f0
> softirqs last disabled at (0): (null)
>
> other info that might help us debug this:
> Possible unsafe locking scenario:
>
> CPU0
> ----
> lock(&sig->group_rwsem);
> <Interrupt>
> lock(&sig->group_rwsem);
>
> *** DEADLOCK ***
>
> no locks held by kswapd2/1151.
>
> stack backtrace:
> CPU: 30 PID: 1151 Comm: kswapd2 Not tainted 3.10.39+ #4
> Call Trace:
> dump_stack+0x19/0x1b
> print_usage_bug+0x1f7/0x208
> mark_lock+0x21d/0x2a0
> __lock_acquire+0x52a/0xb60
> lock_acquire+0xa2/0x140
> down_read+0x51/0xa0
> exit_signals+0x24/0x130
> do_exit+0xb5/0xa50
> kthread+0xdb/0x100
> ret_from_fork+0x7c/0xb0
This is because the kswapd thread is still marked as a reclaimer at the
time of exit. But because it is exiting, nobody is actually waiting on
it to make reclaim progress anymore, and it's nothing but a regular
thread at this point. Be tidy and strip it of all its powers
(PF_MEMALLOC, PF_SWAPWRITE, PF_KSWAPD, and the lockdep reclaim state)
before returning from the thread function.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: Tang Chen <tangchen@cn.fujitsu.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit "mm: vmscan: obey proportional scanning requirements for kswapd"
ensured that file/anon lists were scanned proportionally for reclaim from
kswapd but ignored it for direct reclaim. The intent was to minimse
direct reclaim latency but Yuanhan Liu pointer out that it substitutes one
long stall for many small stalls and distorts aging for normal workloads
like streaming readers/writers. Hugh Dickins pointed out that a
side-effect of the same commit was that when one LRU list dropped to zero
that the entirety of the other list was shrunk leading to excessive
reclaim in memcgs. This patch scans the file/anon lists proportionally
for direct reclaim to similarly age page whether reclaimed by kswapd or
direct reclaim but takes care to abort reclaim if one LRU drops to zero
after reclaiming the requested number of pages.
Based on ext4 and using the Intel VM scalability test
3.15.0-rc5 3.15.0-rc5
shrinker proportion
Unit lru-file-readonce elapsed 5.3500 ( 0.00%) 5.4200 ( -1.31%)
Unit lru-file-readonce time_range 0.2700 ( 0.00%) 0.1400 ( 48.15%)
Unit lru-file-readonce time_stddv 0.1148 ( 0.00%) 0.0536 ( 53.33%)
Unit lru-file-readtwice elapsed 8.1700 ( 0.00%) 8.1700 ( 0.00%)
Unit lru-file-readtwice time_range 0.4300 ( 0.00%) 0.2300 ( 46.51%)
Unit lru-file-readtwice time_stddv 0.1650 ( 0.00%) 0.0971 ( 41.16%)
The test cases are running multiple dd instances reading sparse files. The results are within
the noise for the small test machine. The impact of the patch is more noticable from the vmstats
3.15.0-rc5 3.15.0-rc5
shrinker proportion
Minor Faults 35154 36784
Major Faults 611 1305
Swap Ins 394 1651
Swap Outs 4394 5891
Allocation stalls 118616 44781
Direct pages scanned 4935171 4602313
Kswapd pages scanned 15921292 16258483
Kswapd pages reclaimed 15913301 16248305
Direct pages reclaimed 4933368 4601133
Kswapd efficiency 99% 99%
Kswapd velocity 670088.047 682555.961
Direct efficiency 99% 99%
Direct velocity 207709.217 193212.133
Percentage direct scans 23% 22%
Page writes by reclaim 4858.000 6232.000
Page writes file 464 341
Page writes anon 4394 5891
Note that there are fewer allocation stalls even though the amount
of direct reclaim scanning is very approximately the same.
Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Tested-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Cc: Bob Liu <bob.liu@oracle.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Rik van Riel <riel@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Vladimir Davydov
Hugh Dickins
Jaewon Kim
Michal Hocko
Mel Gorman
Linus Torvalds
Zhihui Zhang
Nishanth Aravamudan
Tejun Heo
Greg Thelen
Johannes Weiner
Vlastimil Babka
Michael S. Tsirkin
Christoph Hellwig
Jamie Liu
Pintu Kumar
Jerome Marchand
Wang Sheng-Hui
Mitchel Humpherys