From: Michael Monnerie <michael.monnerie@is.it-management.at>
To: xfs@oss.sgi.com
Subject: Re: deleting 2TB lots of files with delaylog: sync helps?
Date: Wed, 1 Sep 2010 02:22:31 +0200 [thread overview]
Message-ID: <201009010222.57350@zmi.at> (raw)
In-Reply-To: <20100901000631.GO705@dastard>
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On Mittwoch, 1. September 2010 Dave Chinner wrote:
> You're probably getting RMW cycles on inode writeback. I've been
> noticing this lately with my benchmarking - the VM is being _very
> aggressive_ reclaiming page cache pages vs inode caches and as a
> result the inode buffers used for IO are being reclaimed between the
> time it takes to create the inodes and when they are written back.
> Hence you get lots of reads occurring during inode writeback.
>
> By issuing a sync, you clear out all the inode writeback and all the
> RMW cycles go away. As a result, there is more disk throughput
> availble for the unlink processes. There is a good chance this is
> the case as the number of reads after the sync drop by an order of
> magnitude...
Nice explanation.
> > Now it can be that the sync just causes more writes and stalls
> > reads so overall it's slower, but I'm wondering why none of the
> > devices says "100% util", which should be the case on deletes? Or
> > is this again the "mistake" of the utilization calculation that
> > writes do not really show up there?
>
> You're probably CPU bound, not IO bound.
This is a hexa-core AMD Phenom(tm) II X6 1090T Processor with up to
3.2GHz per core, so that shouldn't be - or is there only one core used?
I think I read somewhere that each AG should get a core or so...
Thanks for your explanation.
--
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next prev parent reply other threads:[~2010-09-01 0:22 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-31 23:30 deleting 2TB lots of files with delaylog: sync helps? Michael Monnerie
2010-09-01 0:06 ` Dave Chinner
2010-09-01 0:22 ` Michael Monnerie [this message]
2010-09-01 3:19 ` Dave Chinner
2010-09-01 4:42 ` Stan Hoeppner
2010-09-01 6:44 ` Dave Chinner
2010-09-02 5:37 ` Stan Hoeppner
2010-09-02 7:01 ` Dave Chinner
2010-09-02 8:41 ` Stan Hoeppner
2010-09-02 11:29 ` Dave Chinner
2010-09-02 14:57 ` Stan Hoeppner
2010-09-01 3:01 ` Stan Hoeppner
2010-09-01 3:41 ` Dave Chinner
2010-09-01 7:45 ` Michael Monnerie
2010-09-02 1:17 ` Dave Chinner
2010-09-02 2:15 ` Michael Monnerie
2010-09-02 7:51 ` Stan Hoeppner
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