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From: Michal Hocko <mhocko@kernel.org>
To: Vinayak Menon <vinmenon@codeaurora.org>
Cc: akpm@linux-foundation.org, hannes@cmpxchg.org,
	mgorman@techsingularity.net, vbabka@suse.cz, riel@redhat.com,
	vdavydov.dev@gmail.com, anton.vorontsov@linaro.org,
	minchan@kernel.org, shashim@codeaurora.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2 v2] mm: vmpressure: fix sending wrong events on underflow
Date: Thu, 9 Feb 2017 13:22:27 +0100	[thread overview]
Message-ID: <20170209122227.GH10257@dhcp22.suse.cz> (raw)
In-Reply-To: <20170209121057.GF10257@dhcp22.suse.cz>

On Thu 09-02-17 13:10:57, Michal Hocko wrote:
> On Thu 09-02-17 17:29:36, Vinayak Menon wrote:
> > At the end of a window period, if the reclaimed pages
> > is greater than scanned, an unsigned underflow can
> > result in a huge pressure value and thus a critical event.
> > Reclaimed pages is found to go higher than scanned because
> > of the addition of reclaimed slab pages to reclaimed in
> > shrink_node without a corresponding increment to scanned
> > pages. Minchan Kim mentioned that this can also happen in
> > the case of a THP page where the scanned is 1 and reclaimed
> > could be 512.
> > 
> > Acked-by: Minchan Kim <minchan@kernel.org>
> > Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>
> 
> Acked-by: Michal Hocko <mhocko@suse.com>
> 
> I would prefer the fixup in vmpressure() as already mentioned but this
> should work as well.

Btw. I guess this should be good to mark for stable. Reclaiming THP is
not all that rare (even though we try to avoid anon reclaim as much as
possible) and hitting critical events can lead to disruptive actions to
early.
-- 
Michal Hocko
SUSE Labs

WARNING: multiple messages have this Message-ID
From: Michal Hocko <mhocko@kernel.org>
To: Vinayak Menon <vinmenon@codeaurora.org>
Cc: akpm@linux-foundation.org, hannes@cmpxchg.org,
	mgorman@techsingularity.net, vbabka@suse.cz, riel@redhat.com,
	vdavydov.dev@gmail.com, anton.vorontsov@linaro.org,
	minchan@kernel.org, shashim@codeaurora.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2 v2] mm: vmpressure: fix sending wrong events on underflow
Date: Thu, 9 Feb 2017 13:22:27 +0100	[thread overview]
Message-ID: <20170209122227.GH10257@dhcp22.suse.cz> (raw)
In-Reply-To: <20170209121057.GF10257@dhcp22.suse.cz>

On Thu 09-02-17 13:10:57, Michal Hocko wrote:
> On Thu 09-02-17 17:29:36, Vinayak Menon wrote:
> > At the end of a window period, if the reclaimed pages
> > is greater than scanned, an unsigned underflow can
> > result in a huge pressure value and thus a critical event.
> > Reclaimed pages is found to go higher than scanned because
> > of the addition of reclaimed slab pages to reclaimed in
> > shrink_node without a corresponding increment to scanned
> > pages. Minchan Kim mentioned that this can also happen in
> > the case of a THP page where the scanned is 1 and reclaimed
> > could be 512.
> > 
> > Acked-by: Minchan Kim <minchan@kernel.org>
> > Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>
> 
> Acked-by: Michal Hocko <mhocko@suse.com>
> 
> I would prefer the fixup in vmpressure() as already mentioned but this
> should work as well.

Btw. I guess this should be good to mark for stable. Reclaiming THP is
not all that rare (even though we try to avoid anon reclaim as much as
possible) and hitting critical events can lead to disruptive actions to
early.
-- 
Michal Hocko
SUSE Labs

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  reply	other threads:[~2017-02-09 12:23 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-02-09 11:59 Vinayak Menon
2017-02-09 11:59 ` Vinayak Menon
2017-02-09 11:59 ` [PATCH 2/2 v5] mm: vmscan: do not pass reclaimed slab to vmpressure Vinayak Menon
2017-02-09 11:59   ` Vinayak Menon
2017-02-09 12:20   ` Michal Hocko
2017-02-09 12:20     ` Michal Hocko
2017-02-10  8:45     ` vinayak menon
2017-02-10  8:45       ` vinayak menon
2017-02-10  9:05       ` Michal Hocko
2017-02-10  9:05         ` Michal Hocko
2017-02-09 12:10 ` [PATCH 1/2 v2] mm: vmpressure: fix sending wrong events on underflow Michal Hocko
2017-02-09 12:10   ` Michal Hocko
2017-02-09 12:22   ` Michal Hocko [this message]
2017-02-09 12:22     ` Michal Hocko

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