linux-kernel - Re: Poor interactive performance with I/O loads with fsync()ing

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Message-ID: <20100323132719.GY5768@kernel.dk>
Date:	Tue, 23 Mar 2010 14:27:19 +0100
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Pawel S <spawels13@...il.com>
Cc:	linux-kernel@...r.kernel.org, Ben Gamari <bgamari.foss@...il.com>,
	tytso <tytso@....edu>, Nick Piggin <npiggin@...e.de>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Poor interactive performance with I/O loads with fsync()ing

On Tue, Mar 23 2010, Pawel S wrote:
> Hello
> 
> I am experiencing very similar issue. My system is a regular desktop
> PC and it suffers from very high I/O latencies (sometimes desktop
> "hangs" for eight seconds or more) when copying large files. I tried
> kernels up to 2.6.34-rc2, but without luck. This issue was raised at
> Phoronix forums and Arjan (from Intel) noticed it can be VM related:
> 
> http://www.phoronix.com/forums/showpost.php?p=114975&postcount=51
> 
> Here is my perf timechart where you can notice I/O "steals" CPU from
> the other tasks:
> 
> http://hotfile.com/dl/30596827/ebe566b/output.svg.gz.html

It's also been my sneaking suspicion that swap is involved. I had lots
of RAM in anything I use, even the laptop and workstation. I'll try and
run some tests with lower memory and force it into swap, I've seen nasty
hangs that way.

-- 
Jens Axboe

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