linux-kernel - Re: Understanding I/O behaviour

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Date:	Wed, 29 Aug 2007 14:43:08 -0700 (PDT)
From:	Martin Knoblauch <spamtrap@...bisoft.de>
To:	Chuck Ebbert <cebbert@...hat.com>, spamtrap@...bisoft.de
Cc:	linux-kernel@...r.kernel.org,
	Peter zijlstra <a.p.zijlstra@...llo.nl>, mingo@...hat.com
Subject: Re: Understanding I/O behaviour - next try


--- Chuck Ebbert <cebbert@...hat.com> wrote:

> On 08/28/2007 11:53 AM, Martin Knoblauch wrote:
> > 
> >  The basic setup is a dual x86_64 box with 8 GB of memory. The
> DL380
> > has a HW RAID5, made from 4x72GB disks and about 100 MB write
> cache.
> > The performance of the block device with O_DIRECT is about 90
> MB/sec.
> > 
> >  The problematic behaviour comes when we are moving large files
> through
> > the system. The file usage in this case is mostly "use once" or
> > streaming. As soon as the amount of file data is larger than 7.5
> GB, we
> > see occasional unresponsiveness of the system (e.g. no more ssh
> > connections into the box) of more than 1 or 2 minutes (!) duration
> > (kernels up to 2.6.19). Load goes up, mainly due to pdflush threads
> and
> > some other poor guys being in "D" state.
> 
> Try booting with "mem=4096M", "mem=2048M", ...
> 
> 

 hmm. I tried 1024M a while ago and IIRC did not see a lot [any]
difference. But as it is no big deal, I will repeat it tomorrow.

 Just curious - what are you expecting? Why should it help?

Thanks
Martin


------------------------------------------------------
Martin Knoblauch
email: k n o b i AT knobisoft DOT de
www:   http://www.knobisoft.de
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