From: Mikulas Patocka <mpatocka@redhat.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: NeilBrown <neilb@suse.com>,
Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org, dm-devel@redhat.com,
Mel Gorman <mgorman@suse.de>,
David Rientjes <rientjes@google.com>,
Ondrej Kozina <okozina@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [dm-devel] [RFC PATCH 2/2] mm, mempool: do not throttle PF_LESS_THROTTLE tasks
Date: Thu, 4 Aug 2016 14:46:07 -0400 (EDT) [thread overview]
Message-ID: <alpine.LRH.2.02.1608041439420.21662@file01.intranet.prod.int.rdu2.redhat.com> (raw)
In-Reply-To: <20160803144229.GD1490@dhcp22.suse.cz>
On Wed, 3 Aug 2016, Michal Hocko wrote:
> > > Even mempool allocations shouldn't allow reclaim to
> > > scan pages too quickly even when LRU lists are full of dirty pages. But
> > > as I've said that would restrict the success rates even under light page
> > > cache load. Throttling on the wait_iff_congested should be quite rare.
> > >
> > > Anyway do you see an excessive throttling with the patch posted
> > > http://lkml.kernel.org/r/20160725192344.GD2166@dhcp22.suse.cz ? Or from
> >
> > It didn't have much effect.
> >
> > Since the patch 4e390b2b2f34b8daaabf2df1df0cf8f798b87ddb (revert of the
> > limitless mempool allocations), swapping to dm-crypt works in the simple
> > example.
>
> OK. Do you see any throttling due to wait_iff_congested?
No, but I've seen occasional stalls of mempool allocations in
throttle_vm_writeout - but the patch that removed throttle_vm_writeout
didn't improve overall speed, so the stalls were only minor.
> writeback_wait_iff_congested trace point should help here. If not maybe
> we should start with the above patch and see how it works in practise.
> If the there is still an excessive and unexpected throttling then we
> should move on to a more mempool/block layer users specific solution.
Currently, dm-crypt reports the device congested only if the underlying
block device is congested.
But as others suggested, dm-crypt should report congested status if is
clogged due to slow encryption progress - and in that case you should not
throttle mempool allocations (because such throttling would decrease
encryption speed even more).
Mikulas
> --
> Michal Hocko
> SUSE Labs
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next prev parent reply other threads:[~2016-08-04 18:46 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-18 8:39 [RFC PATCH 0/2] mempool vs. page allocator interaction Michal Hocko
2016-07-18 8:41 ` [RFC PATCH 1/2] mempool: do not consume memory reserves from the reclaim path Michal Hocko
2016-07-18 8:41 ` [RFC PATCH 2/2] mm, mempool: do not throttle PF_LESS_THROTTLE tasks Michal Hocko
2016-07-19 21:50 ` Mikulas Patocka
2016-07-22 8:46 ` NeilBrown
2016-07-22 9:04 ` NeilBrown
2016-07-22 9:15 ` Michal Hocko
2016-07-23 0:12 ` NeilBrown
2016-07-25 8:32 ` Michal Hocko
2016-07-25 19:23 ` Michal Hocko
2016-07-26 7:07 ` Michal Hocko
2016-07-27 3:43 ` [dm-devel] " NeilBrown
2016-07-27 18:24 ` Michal Hocko
2016-07-27 21:33 ` NeilBrown
2016-07-28 7:17 ` Michal Hocko
2016-08-03 12:53 ` Mikulas Patocka
2016-08-03 14:34 ` Michal Hocko
2016-08-04 18:49 ` Mikulas Patocka
2016-08-12 12:32 ` Michal Hocko
2016-08-13 17:34 ` Mikulas Patocka
2016-08-14 10:34 ` Michal Hocko
2016-08-15 16:15 ` Mikulas Patocka
2016-11-23 21:11 ` Mikulas Patocka
2016-11-24 13:29 ` Michal Hocko
2016-11-24 17:10 ` Mikulas Patocka
2016-11-28 14:06 ` Michal Hocko
2016-07-25 21:52 ` Mikulas Patocka
2016-07-26 7:25 ` Michal Hocko
2016-07-27 4:02 ` [dm-devel] " NeilBrown
2016-07-27 14:28 ` Mikulas Patocka
2016-07-27 18:40 ` Michal Hocko
2016-08-03 13:59 ` Mikulas Patocka
2016-08-03 14:42 ` Michal Hocko
2016-08-04 18:46 ` Mikulas Patocka [this message]
2016-07-27 21:36 ` NeilBrown
2016-07-19 2:00 ` [RFC PATCH 1/2] mempool: do not consume memory reserves from the reclaim path David Rientjes
2016-07-19 7:49 ` Michal Hocko
2016-07-19 13:54 ` Johannes Weiner
2016-07-19 14:19 ` Michal Hocko
2016-07-19 22:01 ` Mikulas Patocka
2016-07-19 20:45 ` David Rientjes
2016-07-20 8:15 ` Michal Hocko
2016-07-20 21:06 ` David Rientjes
2016-07-21 8:52 ` Michal Hocko
2016-07-21 12:13 ` Johannes Weiner
2016-07-21 14:53 ` Michal Hocko
2016-07-21 15:26 ` Johannes Weiner
2016-07-22 1:41 ` NeilBrown
2016-07-22 6:37 ` Michal Hocko
2016-07-22 12:26 ` Vlastimil Babka
2016-07-22 19:44 ` Andrew Morton
2016-07-23 18:52 ` Vlastimil Babka
2016-07-19 21:50 ` Mikulas Patocka
2016-07-20 6:44 ` Michal Hocko
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