From: "Alex Villacís Lasso" <avillaci@fiec.espol.edu.ec>
To: Mel Gorman <mel@csn.ul.ie>
Cc: Andrew Morton <akpm@linux-foundation.org>,
avillaci@ceibo.fiec.espol.edu.ec,
bugzilla-daemon@bugzilla.kernel.org,
Andrea Arcangeli <aarcange@redhat.com>,
bugme-daemon@bugzilla.kernel.org, linux-mm@kvack.org
Subject: Re: [Bugme-new] [Bug 31142] New: Large write to USB stick freezes unrelated tasks for a long time
Date: Fri, 18 Mar 2011 13:05:15 -0500 [thread overview]
Message-ID: <4D839EDB.9080703@fiec.espol.edu.ec> (raw)
In-Reply-To: <20110318111300.GF707@csn.ul.ie>
El 18/03/11 06:13, Mel Gorman escribio:
>
> \o/ ... no wait, it's the other one - :(
>
> If you look at the stack traces though, all of them had called
> do_huge_pmd_anonymous_page() so while it looks similar to 12309, the trigger
> is new because it's THP triggering compaction that is causing the stalls
> rather than page reclaim doing direct writeback which was the culprit in
> the past.
>
> To confirm if this is the case, I'd be very interested in hearing if this
> problem persists in the following cases
>
> 1. 2.6.38-rc8 with defrag disabled by
> echo never>/sys/kernel/mm/transparent_hugepage/defrag
> (this will stop THP allocations calling into compaction)
> 2. 2.6.38-rc8 with THP disabled by
> echo never>
> /sys/kernel/mm/transparent_hugepage/enabled
> (if the problem still persists, then page reclaim is still a problem
> but we should still stop THP doing sync writes)
> 3. 2.6.37 vanilla
> (in case this is a new regression introduced since then)
>
> Migration can do sync writes on dirty pages which is why it looks so similar
> to page reclaim but this can be controlled by the value of sync_migration
> passed into try_to_compact_pages(). If we find that option 1 above makes
> the regression go away or at least helps a lot, then a reasonable fix may
> be to never set sync_migration if __GFP_NO_KSWAPD which is always set for
> THP allocations. I've added Andrea to the cc to see what he thinks.
>
> Thanks for the report.
>
I have just done tests 1 and 2 on 2.6.38 (final, not -rc8), and I have verified that echoing "never" on either /sys/kernel/mm/transparent_hugepage/defrag or /sys/kernel/mm/transparent_hugepage/enabled does allow the file copy to USB to proceed smoothly
(copying 4GB of data). Just to verify, I later wrote "always" to both files, and sure enough, some applications stalled when I repeated the same file copy. So I have at least a workaround for the issue. Given this evidence, will the patch at comment #14
fix the issue for good?
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next prev parent reply other threads:[~2011-03-18 18:06 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <bug-31142-10286@https.bugzilla.kernel.org/>
2011-03-15 20:53 ` Andrew Morton
2011-03-15 22:53 ` Alex Villacís Lasso
2011-03-15 23:19 ` Andrew Morton
2011-03-16 15:25 ` Alex Villacís Lasso
2011-03-16 22:02 ` Andrew Morton
2011-03-17 21:27 ` Alex Villacís Lasso
2011-03-17 21:47 ` Andrew Morton
2011-03-17 22:11 ` Alex Villacís Lasso
2011-03-17 22:25 ` Andrew Morton
2011-03-18 11:13 ` Mel Gorman
2011-03-18 12:26 ` Andrea Arcangeli
2011-03-18 18:05 ` Alex Villacís Lasso [this message]
2011-03-19 13:46 ` Mel Gorman
2011-03-19 16:04 ` Alex Villacís Lasso
2011-03-19 23:51 ` Andrea Arcangeli
2011-03-21 9:41 ` Mel Gorman
2011-03-21 13:48 ` Andrea Arcangeli
2011-03-21 15:22 ` Alex Villacís Lasso
2011-03-21 15:36 ` Alex Villacís Lasso
2011-03-21 15:40 ` Andrea Arcangeli
2011-03-21 16:37 ` Mel Gorman
2011-03-21 17:05 ` Alex Villacís Lasso
2011-03-21 20:16 ` Andrea Arcangeli
2011-03-21 23:35 ` Alex Villacís Lasso
2011-03-22 11:20 ` Mel Gorman
2011-03-22 15:03 ` Andrea Arcangeli
2011-03-22 20:34 ` Alex Villacís Lasso
2011-03-22 21:40 ` Andrea Arcangeli
2011-03-23 0:37 ` Andrea Arcangeli
2011-03-23 16:51 ` Alex Villacís Lasso
2011-04-04 15:37 ` Alex Villacís Lasso
2011-04-08 19:09 ` Andrea Arcangeli
2011-04-08 20:06 ` Alex Villacís Lasso
2011-04-12 16:27 ` Alex Villacís Lasso
2011-04-14 17:25 ` Alex Villacís Lasso
2011-04-14 17:37 ` Andrea Arcangeli
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