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mm, page_alloc: set alloc_flags only once in slowpath 

In __alloc_pages_slowpath(), alloc_flags doesn't change after it's
initialized, so move the initialization above the retry: label.  Also
make the comment above the initialization more descriptive.

The only exception in the alloc_flags being constant is
ALLOC_NO_WATERMARKS, which may change due to TIF_MEMDIE being set on the
allocating thread.  We can fix this, and make the code simpler and a bit
more effective at the same time, by moving the part that determines
ALLOC_NO_WATERMARKS from gfp_to_alloc_flags() to gfp_pfmemalloc_allowed().

This means we don't have to mask out ALLOC_NO_WATERMARKS in numerous
places in __alloc_pages_slowpath() anymore.  The only two tests for the
flag can instead call gfp_pfmemalloc_allowed().

Link: http://lkml.kernel.org/r/20160721073614.24395-3-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Vlastimil Babka 2016-07-28 15:49:13 -07:00 коммит произвёл Linus Torvalds
Родитель 87cc271d5e
Коммит 31a6c1909f
1 изменённых файлов: 26 добавлений и 26 удалений
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52
mm/page_alloc.c
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@ -3119,8 +3119,7 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
*/
count_vm_event(COMPACTSTALL);
page = get_page_from_freelist(gfp_mask, order,
alloc_flags & ~ALLOC_NO_WATERMARKS, ac);
page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
if (page) {
struct zone *zone = page_zone(page);
@ -3288,8 +3287,7 @@ __alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order,
return NULL;
retry:
page = get_page_from_freelist(gfp_mask, order,
alloc_flags & ~ALLOC_NO_WATERMARKS, ac);
page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
/*
* If an allocation failed after direct reclaim, it could be because
@ -3351,16 +3349,6 @@ gfp_to_alloc_flags(gfp_t gfp_mask)
} else if (unlikely(rt_task(current)) && !in_interrupt())
alloc_flags |= ALLOC_HARDER;
if (likely(!(gfp_mask & __GFP_NOMEMALLOC))) {
if (gfp_mask & __GFP_MEMALLOC)
alloc_flags |= ALLOC_NO_WATERMARKS;
else if (in_serving_softirq() && (current->flags & PF_MEMALLOC))
alloc_flags |= ALLOC_NO_WATERMARKS;
else if (!in_interrupt() &&
((current->flags & PF_MEMALLOC) ||
unlikely(test_thread_flag(TIF_MEMDIE))))
alloc_flags |= ALLOC_NO_WATERMARKS;
}
#ifdef CONFIG_CMA
if (gfpflags_to_migratetype(gfp_mask) == MIGRATE_MOVABLE)
alloc_flags |= ALLOC_CMA;
@ -3370,7 +3358,19 @@ gfp_to_alloc_flags(gfp_t gfp_mask)
bool gfp_pfmemalloc_allowed(gfp_t gfp_mask)
{
return !!(gfp_to_alloc_flags(gfp_mask) & ALLOC_NO_WATERMARKS);
if (unlikely(gfp_mask & __GFP_NOMEMALLOC))
return false;
if (gfp_mask & __GFP_MEMALLOC)
return true;
if (in_serving_softirq() && (current->flags & PF_MEMALLOC))
return true;
if (!in_interrupt() &&
((current->flags & PF_MEMALLOC) ||
unlikely(test_thread_flag(TIF_MEMDIE))))
return true;
return false;
}
static inline bool is_thp_gfp_mask(gfp_t gfp_mask)
@ -3503,36 +3503,36 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
(__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)))
gfp_mask &= ~__GFP_ATOMIC;
/*
* The fast path uses conservative alloc_flags to succeed only until
* kswapd needs to be woken up, and to avoid the cost of setting up
* alloc_flags precisely. So we do that now.
*/
alloc_flags = gfp_to_alloc_flags(gfp_mask);
retry:
if (gfp_mask & __GFP_KSWAPD_RECLAIM)
wake_all_kswapds(order, ac);
/*
* OK, we're below the kswapd watermark and have kicked background
* reclaim. Now things get more complex, so set up alloc_flags according
* to how we want to proceed.
*/
alloc_flags = gfp_to_alloc_flags(gfp_mask);
/*
* Reset the zonelist iterators if memory policies can be ignored.
* These allocations are high priority and system rather than user
* orientated.
*/
if ((alloc_flags & ALLOC_NO_WATERMARKS) || !(alloc_flags & ALLOC_CPUSET)) {
if (!(alloc_flags & ALLOC_CPUSET) || gfp_pfmemalloc_allowed(gfp_mask)) {
ac->zonelist = node_zonelist(numa_node_id(), gfp_mask);
ac->preferred_zoneref = first_zones_zonelist(ac->zonelist,
ac->high_zoneidx, ac->nodemask);
}
/* This is the last chance, in general, before the goto nopage. */
page = get_page_from_freelist(gfp_mask, order,
alloc_flags & ~ALLOC_NO_WATERMARKS, ac);
page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
if (page)
goto got_pg;
/* Allocate without watermarks if the context allows */
if (alloc_flags & ALLOC_NO_WATERMARKS) {
if (gfp_pfmemalloc_allowed(gfp_mask)) {
page = get_page_from_freelist(gfp_mask, order,
ALLOC_NO_WATERMARKS, ac);
if (page)