From: Minchan Kim <minchan@kernel.org>
To: Michal Hocko <mhocko@kernel.org>
Cc: Vinayak Menon <vinmenon@codeaurora.org>,
akpm@linux-foundation.org, hannes@cmpxchg.org,
mgorman@techsingularity.net, vbabka@suse.cz, riel@redhat.com,
vdavydov.dev@gmail.com, anton.vorontsov@linaro.org,
shashim@codeaurora.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2 v3] mm: vmscan: do not pass reclaimed slab to vmpressure
Date: Fri, 3 Feb 2017 15:17:37 +0900 [thread overview]
Message-ID: <20170203061737.GA32372@bbox> (raw)
In-Reply-To: <20170202104422.GF22806@dhcp22.suse.cz>
On Thu, Feb 02, 2017 at 11:44:22AM +0100, Michal Hocko wrote:
> On Tue 31-01-17 14:32:08, Vinayak Menon wrote:
> > During global reclaim, the nr_reclaimed passed to vmpressure
> > includes the pages reclaimed from slab. But the corresponding
> > scanned slab pages is not passed. This can cause total reclaimed
> > pages to be greater than scanned, causing an unsigned underflow
> > in vmpressure resulting in a critical event being sent to root
> > cgroup. So do not consider reclaimed slab pages for vmpressure
> > calculation. The reclaimed pages from slab can be excluded because
> > the freeing of a page by slab shrinking depends on each slab's
> > object population, making the cost model (i.e. scan:free) different
> > from that of LRU.
>
> This might be true but what happens if the slab reclaim contributes
> significantly to the overal reclaim? This would be quite rare but not
> impossible.
Of course, it is better for vmpressure to cover slab but it's not
easy without page-based shrinking model, I think. It wold make
vmpressure higher easily due to low reclaim efficiency compared to
LRU pages. Yeah, vmpressure is not a perfect but no need to add
more noises, either. It's regression since 6b4f7799c6a5 so I think
this patch should go first and if someone want to cover slab really,
he should spend a time to work it well. It's too much that Vinayak
shuld make a effort for that.
prev parent reply other threads:[~2017-02-03 6:17 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-27 8:13 [PATCH 1/2 v2] mm: vmscan: do not pass reclaimed slab to vmpressure Vinayak Menon
2017-01-27 8:13 ` [PATCH 2/2] mm: vmpressure: fix sending wrong events on underflow Vinayak Menon
2017-01-30 23:58 ` Minchan Kim
2017-01-30 23:56 ` [PATCH 1/2 v2] mm: vmscan: do not pass reclaimed slab to vmpressure Minchan Kim
2017-01-31 7:48 ` vinayak menon
2017-01-31 9:02 ` [PATCH 1/2 v3] " Vinayak Menon
2017-02-01 6:12 ` Minchan Kim
2017-02-02 10:44 ` Michal Hocko
2017-02-02 10:48 ` Michal Hocko
2017-02-02 11:25 ` vinayak menon
2017-02-02 11:52 ` Michal Hocko
2017-02-02 15:30 ` vinayak menon
2017-02-02 16:01 ` Michal Hocko
2017-02-03 5:26 ` vinayak menon
2017-02-03 14:59 ` Michal Hocko
2017-02-06 11:31 ` vinayak menon
2017-02-02 11:28 ` vinayak menon
2017-02-03 6:17 ` Minchan Kim [this message]
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