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authorMel Gorman <mgorman@techsingularity.net>2017-11-15 17:38:03 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-11-15 18:21:06 -0800
commit453f85d43fa9ee243f0fc3ac4e1be45615301e3f (patch)
treef414b8ef3a3c92903c960225a2ded020a7158494 /kernel/power/snapshot.c
parent2d4894b5d2ae0fe1725ea7abd57b33bfbbe45492 (diff)
download96b-common-453f85d43fa9ee243f0fc3ac4e1be45615301e3f.tar.gz
mm: remove __GFP_COLD
As the page free path makes no distinction between cache hot and cold pages, there is no real useful ordering of pages in the free list that allocation requests can take advantage of. Juding from the users of __GFP_COLD, it is likely that a number of them are the result of copying other sites instead of actually measuring the impact. Remove the __GFP_COLD parameter which simplifies a number of paths in the page allocator. This is potentially controversial but bear in mind that the size of the per-cpu pagelists versus modern cache sizes means that the whole per-cpu list can often fit in the L3 cache. Hence, there is only a potential benefit for microbenchmarks that alloc/free pages in a tight loop. It's even worse when THP is taken into account which has little or no chance of getting a cache-hot page as the per-cpu list is bypassed and the zeroing of multiple pages will thrash the cache anyway. The truncate microbenchmarks are not shown as this patch affects the allocation path and not the free path. A page fault microbenchmark was tested but it showed no sigificant difference which is not surprising given that the __GFP_COLD branches are a miniscule percentage of the fault path. Link: http://lkml.kernel.org/r/20171018075952.10627-9-mgorman@techsingularity.net Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Andi Kleen <ak@linux.intel.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Jan Kara <jack@suse.cz> Cc: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/power/snapshot.c')
-rw-r--r--kernel/power/snapshot.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index a917a301e201..bce0464524d8 100644
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -1884,7 +1884,7 @@ static int enough_free_mem(unsigned int nr_pages, unsigned int nr_highmem)
*/
static inline int get_highmem_buffer(int safe_needed)
{
- buffer = get_image_page(GFP_ATOMIC | __GFP_COLD, safe_needed);
+ buffer = get_image_page(GFP_ATOMIC, safe_needed);
return buffer ? 0 : -ENOMEM;
}
@@ -1945,7 +1945,7 @@ static int swsusp_alloc(struct memory_bitmap *copy_bm,
while (nr_pages-- > 0) {
struct page *page;
- page = alloc_image_page(GFP_ATOMIC | __GFP_COLD);
+ page = alloc_image_page(GFP_ATOMIC);
if (!page)
goto err_out;
memory_bm_set_bit(copy_bm, page_to_pfn(page));