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From: "Jindřich Makovička" <makovick@gmail.com>
To: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mel Gorman <mel@csn.ul.ie>,
	linux-kernel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: khugepaged: gets stuck when writing to USB flash, 2.6.38-rc2
Date: Thu, 3 Feb 2011 22:16:17 +0100	[thread overview]
Message-ID: <AANLkTimRE-=vB=oTFmc64fqJKHUTUT=3X_Gzx78PZ7Xu@mail.gmail.com> (raw)
In-Reply-To: <20110203190612.GL5843@random.random>

On Thu, Feb 3, 2011 at 20:06, Andrea Arcangeli <aarcange@redhat.com> wrote:
> On Thu, Feb 03, 2011 at 01:24:08PM +0000, Mel Gorman wrote:
>> This is very likely. Compaction calls into migration which will wait on
>> dirty pages after a time. With a large number of dirty pages backed by a
>> slow drive such as a USB stick, it could be getting stalled there for a
>> long period of time.
>>
>> Whether migration sleeps or not can be controlled by the sync parameter
>> passed into try_to_compact_memory which could be always forced to false
>> if GFP_NO_KSWAPD?
>
> I would expect that to hide any regression we could have because of
> more dirty cache in the system, yes.
>
> However Jindřich reported not being able to reproduce anything anymore
> in -rc3, so I'm unsure if we should make that change anymore. I asked
> to try again cause it should too easy that got fixed magically

I tried again and reproduced with -rc3 too, sorry for misinformation.

I also tried echo never >  /sys/kernel/mm/transparent_hugepage/defrag
, and it seems preventing the system freeze, but still the copying
itself sometimes comes to almost complete stop (GkrellM shows short
spikes of tens of kB/s on the USB /dev/sdX). In this case, khugepaged
is also in DN. I still didn't observe this problem when disabling THP
completely by echo never > enabled .

-- 
Jindrich Makovicka

  reply	other threads:[~2011-02-03 21:16 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-01-31 19:28 Jindřich Makovička
2011-02-01 15:49 ` Andrea Arcangeli
2011-02-01 21:24   ` Jindřich Makovička
2011-02-02  0:26     ` Andrea Arcangeli
2011-02-03 13:24   ` Mel Gorman
2011-02-03 19:06     ` Andrea Arcangeli
2011-02-03 21:16       ` Jindřich Makovička [this message]
2011-02-04 15:48         ` Andrea Arcangeli
2011-02-13 10:47           ` Jindřich Makovička

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