linux-kernel - Re: [PATCH v2 2/2] virtio_balloon: replace oom notifier with shrinker

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Message-ID: <20180802112901.GH10808@dhcp22.suse.cz>
Date:   Thu, 2 Aug 2018 13:29:01 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Wei Wang <wei.w.wang@...el.com>
Cc:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        virtio-dev@...ts.oasis-open.org, linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, linux-mm@...ck.org,
        mst@...hat.com, akpm@...ux-foundation.org
Subject: Re: [PATCH v2 2/2] virtio_balloon: replace oom notifier with shrinker

On Thu 02-08-18 19:27:40, Wei Wang wrote:
> On 08/02/2018 07:00 PM, Tetsuo Handa wrote:
> > On 2018/08/02 19:32, Wei Wang wrote:
> > > On 08/01/2018 07:34 PM, Michal Hocko wrote:
> > > > Do you have any numbers for how does this work in practice?
> > > It works in this way: for example, we can set the parameter, balloon_pages_to_shrink,
> > > to shrink 1GB memory once shrink scan is called. Now, we have a 8GB guest, and we balloon
> > > out 7GB. When shrink scan is called, the balloon driver will get back 1GB memory and give
> > > them back to mm, then the ballooned memory becomes 6GB.
> > Since shrinker might be called concurrently (am I correct?),
> 
> Not sure about it being concurrently, but I think it would be called
> repeatedly as should_continue_reclaim() returns true.

Multiple direct reclaimers might indeed invoke it concurrently.
-- 
Michal Hocko
SUSE Labs