linux-kernel - Re: Debugging system freezes on filesystem writes

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Message-ID: <509D014B.2080709@hibox.fi>
Date:	Fri, 09 Nov 2012 15:12:43 +0200
From:	Marcus Sundman <marcus@...ox.fi>
To:	Jan Kara <jack@...e.cz>
CC:	linux-kernel@...r.kernel.org
Subject: Re: Debugging system freezes on filesystem writes

On 09.11.2012 01:41, Marcus Sundman wrote:
> On 07.11.2012 18:17, Jan Kara wrote:
>> On Fri 02-11-12 04:19:24, Marcus Sundman wrote:
>>> Also, and this might be important, according to iotop there is
>>> almost no disk writing going on during the freeze. (Occasionally
>>> there are a few MB/s, but mostly it's 0-200 kB/s.) Well, at least
>>> when an iotop running on nice -20 hasn't frozen completely, which it
>>> does during the more severe freezes.
>>    OK, it seems as if your machine has some problems with memory
>> allocations. Can you capture /proc/vmstat before the freeze and after 
>> the
>> freeze and send them for comparison. Maybe it will show us what is the
>> system doing.
>
> t=01:06 http://sundman.iki.fi/vmstat.pre-freeze.txt
> t=01:08 http://sundman.iki.fi/vmstat.during-freeze.txt
> t=01:12 http://sundman.iki.fi/vmstat.post-freeze.txt

Here are some more vmstats:
http://sundman.iki.fi/vmstats.tar.gz

They are from running this:
while true; do cat /proc/vmstat > "vmstat.$(date +%FT%X).txt"; sleep 10; 
done

There were lots and lots of freezes for almost 20 mins from 14:37:45 
onwards, pretty much constantly, but at 14:56:50 the freezes suddenly 
stopped and everything went back to how it should be.


Thanks,
Marcus

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