linux-kernel - Re: [PATCH v2] mm: fix condition for throttle_direct

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Date:   Tue, 14 Mar 2017 11:04:42 +0800
From:   "Hillf Danton" <hillf.zj@...baba-inc.com>
To:     "'Shakeel Butt'" <shakeelb@...gle.com>,
        "'Johannes Weiner'" <hannes@...xchg.org>,
        "'Mel Gorman'" <mgorman@...hsingularity.net>,
        "'Michal Hocko'" <mhocko@...e.com>,
        "'Vlastimil Babka'" <vbabka@...e.cz>,
        "'Andrew Morton'" <akpm@...ux-foundation.org>
Cc:     "'Jia He'" <hejianet@...il.com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] mm: fix condition for throttle_direct_reclaim


On March 14, 2017 6:19 AM Shakeel Butt wrote: 
> 
> Recently kswapd has been modified to give up after MAX_RECLAIM_RETRIES
> number of unsucessful iterations. Before going to sleep, kswapd thread
> will unconditionally wakeup all threads sleeping on pfmemalloc_wait.
> However the awoken threads will recheck the watermarks and wake the
> kswapd thread and sleep again on pfmemalloc_wait. There is a chance
> of continuous back and forth between kswapd and direct reclaiming
> threads if the kswapd keep failing and thus defeat the purpose of
> adding backoff mechanism to kswapd. So, add kswapd_failures check
> on the throttle_direct_reclaim condition.
> 
> Signed-off-by: Shakeel Butt <shakeelb@...gle.com>
> Suggested-by: Michal Hocko <mhocko@...e.com>
> Suggested-by: Johannes Weiner <hannes@...xchg.org>
> ---

Acked-by: Hillf Danton <hillf.zj@...baba-inc.com>