linux-kernel - Re: [PATCH] mm/vmscan: don't scan adjust too much if current is not kswapd

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Message-ID: <20220921091303.hihmb3qvfvl3s365@techsingularity.net>
Date:   Wed, 21 Sep 2022 10:13:03 +0100
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Hongchen Zhang <zhanghongchen@...ngson.cn>
Cc:     Mel Gorman <mgorman@...e.de>, Matthew Wilcox <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/vmscan: don't scan adjust too much if current is not
 kswapd

On Tue, Sep 20, 2022 at 10:23:05AM +0800, Hongchen Zhang wrote:
> Hi Mel,
> 
> The scan adjust algorithm was originally introduced by you from
> commmit e82e0561dae9 ("mm: vmscan: obey proportional scanning requirements
> for kswapd"), any suggestion about this fix patch?
> In short, proportional scanning is not friendly to processes other than
> kswapd.
> 

I suspect that 6eb90d649537 ("mm: vmscan: fix extreme overreclaim and swap
floods") is a more appropriate fix. While it also has a fairness impact,
it's a more general approach that is likely more robust and while
fairness is important, completely thrashing a full LRU is neither fair
nor expected.

-- 
Mel Gorman
SUSE Labs