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SubjectRe: [resend][PATCH] mm, vmscan: fix do_try_to_free_pages() livelock
(2012/06/14 17:13), kosaki.motohiro@gmail.com wrote:
> From: KOSAKI Motohiro<kosaki.motohiro@jp.fujitsu.com>
>
> Currently, do_try_to_free_pages() can enter livelock. Because of,
> now vmscan has two conflicted policies.
>
> 1) kswapd sleep when it couldn't reclaim any page when reaching
> priority 0. This is because to avoid kswapd() infinite
> loop. That said, kswapd assume direct reclaim makes enough
> free pages to use either regular page reclaim or oom-killer.
> This logic makes kswapd -> direct-reclaim dependency.
> 2) direct reclaim continue to reclaim without oom-killer until
> kswapd turn on zone->all_unreclaimble. This is because
> to avoid too early oom-kill.
> This logic makes direct-reclaim -> kswapd dependency.
>
> In worst case, direct-reclaim may continue to page reclaim forever
> when kswapd sleeps forever.
>
> We can't turn on zone->all_unreclaimable from direct reclaim path
> because direct reclaim path don't take any lock and this way is racy.
>
> Thus this patch removes zone->all_unreclaimable field completely and
> recalculates zone reclaimable state every time.
>
> Note: we can't take the idea that direct-reclaim see zone->pages_scanned
> directly and kswapd continue to use zone->all_unreclaimable. Because, it
> is racy. commit 929bea7c71 (vmscan: all_unreclaimable() use
> zone->all_unreclaimable as a name) describes the detail.
>
> Reported-by: Aaditya Kumar<aaditya.kumar.30@gmail.com>
> Reported-by: Ying Han<yinghan@google.com>
> Cc: Nick Piggin<npiggin@gmail.com>
> Acked-by: Rik van Riel<riel@redhat.com>
> Cc: Michal Hocko<mhocko@suse.cz>
> Cc: Johannes Weiner<hannes@cmpxchg.org>
> Cc: Mel Gorman<mel@csn.ul.ie>
> Cc: KAMEZAWA Hiroyuki<kamezawa.hiroyu@jp.fujitsu.com>
> Cc: Minchan Kim<minchan.kim@gmail.com>
> Signed-off-by: KOSAKI Motohiro<kosaki.motohiro@jp.fujitsu.com>

I like this.
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>



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