linux-kernel - Re: direct-io regression [Was: How to track down abysmal performance ata - raid1 - crypto - vg/lv

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Message-ID: <20100805155357.GA8245@comet.dominikbrodowski.net>
Date:	Thu, 5 Aug 2010 17:53:57 +0200
From:	Dominik Brodowski <linux@...inikbrodowski.net>
To:	Chris Mason <chris.mason@...cle.com>
Cc:	josef@...hat.com, Valdis.Kletnieks@...edu,
	Michael Monnerie <michael.monnerie@...it-management.at>,
	Christoph Hellwig <hch@...radead.org>,
	linux-raid@...r.kernel.org, xfs@....sgi.com,
	linux-kernel@...r.kernel.org, dm-devel@...hat.com
Subject: Re: direct-io regression [Was: How to track down abysmal
 performance ata - raid1 - crypto - vg/lv - xfs]

On Thu, Aug 05, 2010 at 11:39:43AM -0400, Chris Mason wrote:
> On Thu, Aug 05, 2010 at 05:35:19PM +0200, Dominik Brodowski wrote:
> > On Thu, Aug 05, 2010 at 07:32:40AM -0400, Chris Mason wrote:
> > > But, I'm surprised your drive is doing 8K dio reads at 16MB/s, that
> > > seems a little high.  
> > 
> > Well, that's what it does:
> > 
> > # $ dd if=/dev/mapper/vg0-home_crypt of=/dev/zero iflag=direct bs=8k count=131072 seek=131072
> > # 131072+0 records in
> > # 131072+0 records out
> > # 1073741824 bytes (1.1 GB) copied, 62.0177 s, 17.3 MB/s
> 
> Can I ask you to do the test directly to the real honest to goodness
> drive?   If it were an SSD I'd be less surprised, but then the extra
> submits shouldn't hurt the ssd that much either.

>From lower the chain up to the device:

# LANG=EN dd if=/dev/mapper/vg0-root_crypt of=/dev/zero bs=8k count=131072 seek=393300 iflag=direct
131072+0 records in
131072+0 records out
1073741824 bytes (1.1 GB) copied, 63.1217 s, 17.0 MB/s

# LANG=EN dd if=/dev/mapper/vg0-root of=/dev/zero bs=8k count=131072 seek=393300 iflag=direct
131072+0 records in
131072+0 records out
1073741824 bytes (1.1 GB) copied, 43.2335 s, 24.8 MB/s

# LANG=EN dd if=/dev/sda5 of=/dev/zero bs=8k count=131072 seek=393300 iflag=direct
131072+0 records in
131072+0 records out
1073741824 bytes (1.1 GB) copied, 42.0868 s, 25.5 MB/s

Best,
	Dominik
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