From: Michal Hocko <mhocko@kernel.org>
To: Minchan Kim <minchan@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
Miguel de Dios <migueldedios@google.com>,
Wei Wang <wvw@google.com>, Johannes Weiner <hannes@cmpxchg.org>,
Mel Gorman <mgorman@techsingularity.net>
Subject: Re: [PATCH] mm: release the spinlock on zap_pte_range
Date: Mon, 29 Jul 2019 10:35:15 +0200 [thread overview]
Message-ID: <20190729083515.GD9330@dhcp22.suse.cz> (raw)
In-Reply-To: <20190729082052.GA258885@google.com>
On Mon 29-07-19 17:20:52, Minchan Kim wrote:
> On Mon, Jul 29, 2019 at 09:45:23AM +0200, Michal Hocko wrote:
> > On Mon 29-07-19 16:10:37, Minchan Kim wrote:
> > > In our testing(carmera recording), Miguel and Wei found unmap_page_range
> > > takes above 6ms with preemption disabled easily. When I see that, the
> > > reason is it holds page table spinlock during entire 512 page operation
> > > in a PMD. 6.2ms is never trivial for user experince if RT task couldn't
> > > run in the time because it could make frame drop or glitch audio problem.
> >
> > Where is the time spent during the tear down? 512 pages doesn't sound
> > like a lot to tear down. Is it the TLB flushing?
>
> Miguel confirmed there is no such big latency without mark_page_accessed
> in zap_pte_range so I guess it's the contention of LRU lock as well as
> heavy activate_page overhead which is not trivial, either.
Please give us more details ideally with some numbers.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-07-29 8:35 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-29 7:10 [PATCH] mm: release the spinlock on zap_pte_range Minchan Kim
2019-07-29 7:45 ` Michal Hocko
2019-07-29 8:20 ` Minchan Kim
2019-07-29 8:35 ` Michal Hocko [this message]
2019-07-30 12:11 ` Minchan Kim
2019-07-30 12:32 ` Michal Hocko
2019-07-30 12:39 ` Minchan Kim
2019-07-30 12:57 ` Michal Hocko
2019-07-31 5:44 ` Minchan Kim
2019-07-31 7:21 ` Michal Hocko
2019-08-06 10:55 ` Minchan Kim
2019-08-09 12:43 ` [RFC PATCH] mm: drop mark_page_access from the unmap path Michal Hocko
2019-08-09 17:57 ` Mel Gorman
2019-08-09 18:34 ` Johannes Weiner
2019-08-12 8:09 ` Michal Hocko
2019-08-12 15:07 ` Johannes Weiner
2019-08-13 10:51 ` Michal Hocko
2019-08-26 12:06 ` Michal Hocko
2019-08-27 16:00 ` Johannes Weiner
2019-08-27 18:41 ` Michal Hocko
2019-07-30 19:42 ` [PATCH] mm: release the spinlock on zap_pte_range Andrew Morton
2019-07-31 6:14 ` Minchan Kim
2019-08-06 7:05 ` [mm] 755d6edc1a: will-it-scale.per_process_ops -4.1% regression kernel test robot
[not found] ` <20190806080415.GG11812@dhcp22.suse.cz>
2019-08-06 11:00 ` Minchan Kim
2019-08-06 11:11 ` Michal Hocko
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