From: Mel Gorman <mgorman@suse.de>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
David Rientjes <rientjes@google.com>,
linux-kernel@vger.kernel.org, Minchan Kim <minchan@kernel.org>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Michal Nazarewicz <mina86@mina86.com>,
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
Christoph Lameter <cl@linux.com>, Rik van Riel <riel@redhat.com>,
Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Subject: Re: [PATCH V4 01/15] mm, THP: don't hold mmap_sem in khugepaged when allocating THP
Date: Fri, 25 Jul 2014 13:18:15 +0100 [thread overview]
Message-ID: <20140725121815.GV10819@suse.de> (raw)
In-Reply-To: <1405518503-27687-2-git-send-email-vbabka@suse.cz>
On Wed, Jul 16, 2014 at 03:48:09PM +0200, Vlastimil Babka wrote:
> 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 also deletes an outdated comment that assumed vma must be stable, as it was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 9f1b868a13
> ("mm: thp: khugepaged: add policy for finding target node").
>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@suse.de>
--
Mel Gorman
SUSE Labs
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next prev parent reply other threads:[~2014-07-25 12:18 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-16 13:48 [PATCH V4 00/15] compaction: balancing overhead and success rates Vlastimil Babka
2014-07-16 13:48 ` [PATCH V4 01/15] mm, THP: don't hold mmap_sem in khugepaged when allocating THP Vlastimil Babka
2014-07-25 12:18 ` Mel Gorman [this message]
2014-07-16 13:48 ` [PATCH V4 02/15] mm, compaction: defer each zone individually instead of preferred zone Vlastimil Babka
2014-07-25 12:20 ` Mel Gorman
2014-07-16 13:48 ` [PATCH V4 03/15] mm, compaction: do not count compact_stall if all zones skipped compaction Vlastimil Babka
2014-07-25 12:22 ` Mel Gorman
2014-07-16 13:48 ` [PATCH V4 04/15] mm, compaction: do not recheck suitable_migration_target under lock Vlastimil Babka
2014-07-25 12:23 ` Mel Gorman
2014-07-16 13:48 ` [PATCH V4 05/15] mm, compaction: move pageblock checks up from isolate_migratepages_range() Vlastimil Babka
2014-07-25 12:28 ` Mel Gorman
2014-07-16 13:48 ` [PATCH V4 06/15] mm, compaction: reduce zone checking frequency in the migration scanner Vlastimil Babka
2014-07-25 12:29 ` Mel Gorman
2014-07-16 13:48 ` [PATCH V4 07/15] mm, compaction: khugepaged should not give up due to need_resched() Vlastimil Babka
2014-07-25 12:31 ` Mel Gorman
2014-07-16 13:48 ` [PATCH V4 08/15] mm, compaction: periodically drop lock and restore IRQs in scanners Vlastimil Babka
2014-07-25 12:32 ` Mel Gorman
2014-07-16 13:48 ` [PATCH V4 09/15] mm, compaction: skip rechecks when lock was already held Vlastimil Babka
2014-07-25 12:34 ` Mel Gorman
2014-07-16 13:48 ` [PATCH V4 10/15] mm, compaction: remember position within pageblock in free pages scanner Vlastimil Babka
2014-07-25 12:35 ` Mel Gorman
2014-07-16 13:48 ` [PATCH V4 11/15] mm, compaction: skip buddy pages by their order in the migrate scanner Vlastimil Babka
2014-07-25 12:36 ` Mel Gorman
2014-07-16 13:48 ` [PATCH V4 12/15] mm: rename allocflags_to_migratetype for clarity Vlastimil Babka
2014-07-25 12:37 ` Mel Gorman
2014-07-16 13:48 ` [PATCH V4 13/15] mm, compaction: pass gfp mask to compact_control Vlastimil Babka
2014-07-25 12:38 ` Mel Gorman
2014-07-16 13:48 ` [PATCH V4 14/15] mm, compaction: try to capture the just-created high-order freepage Vlastimil Babka
2014-07-25 12:56 ` Mel Gorman
2014-07-25 15:49 ` Vlastimil Babka
2014-07-16 13:48 ` [RFC PATCH V4 15/15] mm, compaction: do not migrate pages when that cannot satisfy page fault allocation Vlastimil Babka
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