linux-kernel - Re: [PATCH 6/9] mm: don't avoid high-priority reclaim on memcg limit reclaim

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Message-ID: <078101d29305$aa290420$fe7b0c60$@alibaba-inc.com>
Date:   Thu, 02 Mar 2017 11:32:47 +0800
From:   "Hillf Danton" <hillf.zj@...baba-inc.com>
To:     "'Johannes Weiner'" <hannes@...xchg.org>,
        "'Andrew Morton'" <akpm@...ux-foundation.org>
Cc:     "'Jia He'" <hejianet@...il.com>, "'Michal Hocko'" <mhocko@...e.cz>,
        "'Mel Gorman'" <mgorman@...e.de>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>, <kernel-team@...com>
Subject: Re: [PATCH 6/9] mm: don't avoid high-priority reclaim on memcg limit reclaim

On March 01, 2017 5:40 AM Johannes Weiner wrote: 
> 
> 246e87a93934 ("memcg: fix get_scan_count() for small targets") sought
> to avoid high reclaim priorities for memcg by forcing it to scan a
> minimum amount of pages when lru_pages >> priority yielded nothing.
> This was done at a time when reclaim decisions like dirty throttling
> were tied to the priority level.
> 
> Nowadays, the only meaningful thing still tied to priority dropping
> below DEF_PRIORITY - 2 is gating whether laptop_mode=1 is generally
> allowed to write. But that is from an era where direct reclaim was
> still allowed to call ->writepage, and kswapd nowadays avoids writes
> until it's scanned every clean page in the system. Potential changes
> to how quick sc->may_writepage could trigger are of little concern.
> 
> Remove the force_scan stuff, as well as the ugly multi-pass target
> calculation that it necessitated.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
> ---
Acked-by: Hillf Danton <hillf.zj@...baba-inc.com>