linux-kernel - Re: [RFC PATCH 1/2] mm, vmscan: account the number of isolated pages per zone

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Date:   Thu, 2 Feb 2017 11:14:15 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:     hch@....de, mgorman@...e.de, viro@...IV.linux.org.uk,
        linux-mm@...ck.org, hannes@...xchg.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 1/2] mm, vmscan: account the number of isolated pages
 per zone

On Mon 30-01-17 09:55:46, Michal Hocko wrote:
> On Sun 29-01-17 00:27:27, Tetsuo Handa wrote:
[...]
> > Regarding [1], it helped avoiding the too_many_isolated() issue. I can't
> > tell whether it has any negative effect, but I got on the first trial that
> > all allocating threads are blocked on wait_for_completion() from flush_work()
> > in drain_all_pages() introduced by "mm, page_alloc: drain per-cpu pages from
> > workqueue context". There was no warn_alloc() stall warning message afterwords.
> 
> That patch is buggy and there is a follow up [1] which is not sitting in the
> mmotm (and thus linux-next) yet. I didn't get to review it properly and
> I cannot say I would be too happy about using WQ from the page
> allocator. I believe even the follow up needs to have WQ_RECLAIM WQ.
> 
> [1] http://lkml.kernel.org/r/20170125083038.rzb5f43nptmk7aed@techsingularity.net

Did you get chance to test with this follow up patch? It would be
interesting to see whether OOM situation can still starve the waiter.
The current linux-next should contain this patch.

Thanks!
-- 
Michal Hocko
SUSE Labs