From mboxrd@z Thu Jan  1 00:00:00 1970
From: Chris Down <chris-6Bi1550iOqEnzZ6mRAm98g@public.gmane.org>
Subject: Re: [PATCH] mm, memcg: reclaim more aggressively before high
 allocator throttling
Date: Thu, 28 May 2020 22:14:41 +0100
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To: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
Cc: Shakeel Butt <shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Linux MM <linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org>, Cgroups <cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Kernel Team <kernel-team-b10kYP2dOMg@public.gmane.org>

Johannes Weiner writes:
>> I don't feel strongly either way, but current->memcg_nr_pages_over_high can
>> be very large for large allocations.
>>
>> That said, maybe we should just reclaim `max(SWAP_CLUSTER_MAX, current -
>> high)` for each loop? I agree that with this design it looks like perhaps we
>> don't need it any more.
>>
>> Johannes, what do you think?
>
>How about this:
>
>Reclaim memcg_nr_pages_over_high in the first iteration, then switch
>to SWAP_CLUSTER_MAX in the retries.
>
>This acknowledges that while the page allocator and memory.max reclaim
>every time an allocation is made, memory.high is currently batched and
>can have larger targets. We want the allocating thread to reclaim at
>least the batch size, but beyond that only what's necessary to prevent
>premature OOM or failing containment.
>
>Add a comment stating as much.
>
>Once we reclaim memory.high synchronously instead of batched, this
>exceptional handling is no longer needed and can be deleted again.
>
>Does that sound reasonable?

That sounds good to me, thanks. I'll change that in v2 soonish and update the 
changelog.