Commit b121186a authored Aug 21, 2012 by Alex Shi Committed by Linus Torvalds Aug 21, 2012

mm: correct page->pfmemalloc to fix deactivate_slab regression



Commit cfd19c5a ("mm: only set page->pfmemalloc when
ALLOC_NO_WATERMARKS was used") tried to narrow down page->pfmemalloc
setting, but it missed some places the pfmemalloc should be set.

So, in __slab_alloc, the unalignment pfmemalloc and ALLOC_NO_WATERMARKS
cause incorrect deactivate_slab() on our core2 server:

    64.73%           fio  [kernel.kallsyms]     [k] _raw_spin_lock
                     |
                     --- _raw_spin_lock
                        |
                        |---0.34%-- deactivate_slab
                        |          __slab_alloc
                        |          kmem_cache_alloc
                        |          |

That causes our fio sync write performance to have a 40% regression.

Move the checking in get_page_from_freelist() which resolves this issue.

Signed-off-by: Alex Shi <alex.shi@intel.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: David Miller <davem@davemloft.net
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: Eric Dumazet <eric.dumazet@gmail.com>
Tested-by: Sage Weil <sage@inktank.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 5ed12f12

mm/page_alloc.c

+11 −10

Original line number	Diff line number	Diff line
		@@ -1928,6 +1928,17 @@ this_zone_full:
		zlc_active = 0;
		goto zonelist_scan;
		}

		if (page)
		/*
		* page->pfmemalloc is set when ALLOC_NO_WATERMARKS was
		* necessary to allocate the page. The expectation is
		* that the caller is taking steps that will free more
		* memory. The caller should avoid the page being used
		* for !PFMEMALLOC purposes.
		*/
		page->pfmemalloc = !!(alloc_flags & ALLOC_NO_WATERMARKS);

		return page;
		}

		@@ -2389,14 +2400,6 @@ rebalance:
		zonelist, high_zoneidx, nodemask,
		preferred_zone, migratetype);
		if (page) {
		/*
		* page->pfmemalloc is set when ALLOC_NO_WATERMARKS was
		* necessary to allocate the page. The expectation is
		* that the caller is taking steps that will free more
		* memory. The caller should avoid the page being used
		* for !PFMEMALLOC purposes.
		*/
		page->pfmemalloc = true;
		goto got_pg;
		}
		}
		@@ -2569,8 +2572,6 @@ retry_cpuset:
		page = __alloc_pages_slowpath(gfp_mask, order,
		zonelist, high_zoneidx, nodemask,
		preferred_zone, migratetype);
		else
		page->pfmemalloc = false;

		trace_mm_page_alloc(page, order, gfp_mask, migratetype);

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