Currently, we crash (issue BUG_ON) if backing swap
disk size is zero. This can happen is user specified
an extended partition or simply a bad disk as backing
swap. A crash is really an unpleasant surprise to user
for such trivial problems.
Now, we check for this condition and simply fail device
initialization if this is the case.
Additional cleanups:
* use static for all functions
* remove extra newline between functions
* memset backing_swap_name to NULL on device reset
Signed-off-by: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
ramzswap_free_page() already handles the case for zero filled
pages. So, remove redundant logic for the same in ramzswap_write().
Signed-off-by: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Currently, we return 0 if create_device() fails and 1 otherwise.
Now, proper error code is returned from create_device() and the
same is propagated as module error code from ramzswap_init().
Also added some cleanups for ramzswap_init(), improving function
structure.
Signed-off-by: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
ramzswap block size needs to be set equal to PAGE_SIZE to
avoid receiving any unaligned block I/O requests (happens
due to readahead logic during swapon). These unaligned
accesses produce unnecessary I/O errors, scaring users.
Signed-off-by: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Make sure we flush block device before freeing all metadata
during reset ioctl.
Signed-off-by: Nitin Gupta <ngupta@vflar.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
64-bit stats corruption was observed when ramzswap was
used on SMP systems. To prevent this, use separate spinlock
to protect these stats.
Also, replace stat_*() with rzs_stat*() to avoid possible
conflict with core kernel code.
Eventually, these will be converted to per-cpu counters
if this driver finds use on large scale systems and this
locking is found to affect scalability.
Signed-off-by: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
If create_device is failed, it can't free gendisk and request_queue of
preceding devices. It cause memory leak.
This patch fixes it.
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Remove d-cache hack in ramzswap driver that was needed
to workaround a bug in ARM version of update_mmu_cache()
which caused stale data in d-cache to be transferred to
userspace. This bug was fixed by git commit:
787b2faadc
This also brings down one entry in TODO file.
Signed-off-by: Nitin Gupta <ngupta@vflare.org>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Creates RAM based block devices (/dev/ramzswapX) which can be
used (only) as swap disks. Pages swapped to these are compressed
and stored in memory itself.
The module is called ramzswap.ko. It depends on:
- xvmalloc memory allocator (compiled with this driver)
- lzo_compress.ko
- lzo_decompress.ko
See ramzswap.txt for usage details.
Signed-off-by: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
* Features:
- Low metadata overhead (just 4 bytes per object)
- O(1) Alloc/Free - except when we have to call system page allocator to
get additional memory.
- Very low fragmentation: In all tests, xvmalloc memory usage is within 12%
of "Ideal".
- Pool based allocator: Each pool can grow and shrink.
- It maps pages only when required. So, it does not hog vmalloc area which
is very small on 32-bit systems.
SLUB allocator could not be used due to fragmentation issues:
http://code.google.com/p/compcache/wiki/AllocatorsComparison
Data here shows kmalloc using ~43% more memory than TLSF and xvMalloc
is showed ~2% more space efficiency than TLSF (due to smaller metadata).
Creating various kmem_caches can reduce space efficiency gap but still
problem of being limited to low memory exists. Also, it depends on
allocating higher order pages to reduce fragmentation - this is not
acceptable for ramzswap as it is used under memory crunch (its a swap
device!).
SLOB allocator could not be used do to reasons mentioned here:
http://lkml.org/lkml/2009/3/18/210
* Implementation:
It uses two-level bitmap search to find free list containing block of
correct size. This idea is taken from TLSF (Two-Level Segregate Fit)
allocator and is well explained in its paper (see [Links] below).
* Limitations:
- Poor scalability: No per-cpu data structures (work in progress).
[Links]
1. Details and Performance data:
http://code.google.com/p/compcache/wiki/xvMallochttp://code.google.com/p/compcache/wiki/xvMallocPerformance
2. TLSF memory allocator:
home: http://rtportal.upv.es/rtmalloc/
paper: http://rtportal.upv.es/rtmalloc/files/MRBC_2008.pdf
Signed-off-by: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Nitin Gupta
Minchan Kim
C yp
Huang Weiyi