linux-kernel - Re: Reclaim regression after 1c30844d2dfe

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Message-ID: <20200212235525.GU3466@techsingularity.net>
Date:   Wed, 12 Feb 2020 23:55:25 +0000
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Ivan Babrou <ivan@...udflare.com>
Cc:     linux-mm@...ck.org, linux-kernel <linux-kernel@...r.kernel.org>,
        kernel-team <kernel-team@...udflare.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Rik van Riel <riel@...riel.com>,
        Vlastimil Babka <vbabka@...e.cz>
Subject: Re: Reclaim regression after 1c30844d2dfe

On Wed, Feb 12, 2020 at 02:45:39PM -0800, Ivan Babrou wrote:
> Here's a typical graph: https://imgur.com/a/n03x5yH
> 
> * Green (numa0) and blue (numa1) for 4.19
> * Yellow (numa0) and orange (numa1) for 5.4
> 
> These downward slopes on numa0 on 5.4 are somewhat typical to the
> worst case scenario.
> 
> If I try to clean up data a bit from a bunch of machines, this is how
> numa0 compares to numa1 with 1h average values of free memory above
> 5GiB:
> 
> * https://imgur.com/a/6T4rRzi
> 
> I think it's safe to say that numa0 is much much worse, but I cannot
> be 100% sure that numa1 is free from adverse effects, they may be just
> hiding in the noise caused by rolling reboots.
> 

Ok, while I expected node 0 to be worse in general, a runaway boost due
to constant fragmentation would be a problem in general. In either case,
the patch should reduce the damage. Is there any chance that the patch
can be tested or would it be disruptive for you?

-- 
Mel Gorman
SUSE Labs