linux-kernel - Re: Strange write starvation on 2.6.17 (and other) kernels

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Date:	Mon, 21 Aug 2006 11:31:20 +1000
From:	Neil Brown <neilb@...e.de>
To:	"Miquel van Smoorenburg" <miquels@...tron.nl>
Cc:	linux-kernel@...r.kernel.org,
	Andrzej Szymanski <szymans@....edu.pl>
Subject: Re: Strange write starvation on 2.6.17 (and other) kernels

On Thursday August 17, miquels@...tron.nl wrote:
> In article <44E0A69C.5030103@....edu.pl>,
> Andrzej Szymanski  <szymans@....edu.pl> wrote:
> >I've encountered a strange problem - if an application is sequentially 
> >writing a large file on a busy machine, a single write() of 64KB may 
> >take even 30 seconds. But if I do fsync() after each write() the maximum 
> >time of write()+fsync() is about 0.5 second (the overall performance is, 
> >of course, degraded).
> 
> I'm seeing something similar.

Can you report the contents of /proc/meminfo before, during, and after
the long pause?
I'm particularly interested in MemTotal, Dirty, and Writeback, but the
others are of interest too.

Thanks,
NeilBrown
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