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authorVlastimil Babka <vbabka@suse.cz>2014-10-09 15:27:00 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-10-09 22:25:53 -0400
commit8b1645685acf3c7e0b93611fb4b328ef45c47e92 (patch)
tree2446890b39f06e4ddbe6101e0644fb969a790b80 /mm/compaction.c
parent447f05bb488bff4282088259b04f47f0f9f76760 (diff)
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mm, THP: don't hold mmap_sem in khugepaged when allocating THP
When allocating huge page for collapsing, khugepaged currently holds mmap_sem for reading on the mm where collapsing occurs. Afterwards the read lock is dropped before write lock is taken on the same mmap_sem. Holding mmap_sem during whole huge page allocation is therefore useless, the vma needs to be rechecked after taking the write lock anyway. Furthemore, huge page allocation might involve a rather long sync compaction, and thus block any mmap_sem writers and i.e. affect workloads that perform frequent m(un)map or mprotect oterations. This patch simply releases the read lock before allocating a huge page. It also deletes an outdated comment that assumed vma must be stable, as it was using alloc_hugepage_vma(). This is no longer true since commit 9f1b868a13ac ("mm: thp: khugepaged: add policy for finding target node"). Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Cc: Minchan Kim <minchan@kernel.org> 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> 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>
Diffstat (limited to 'mm/compaction.c')
0 files changed, 0 insertions, 0 deletions
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