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Date: Thu, 5 Aug 2010 18:35:19 +0200
From: Dominik Brodowski <linux@dominikbrodowski.net>
To: Chris Mason <chris.mason@oracle.com>, josef@redhat.com,
        Valdis.Kletnieks@vt.edu,
        Michael Monnerie <michael.monnerie@is.it-management.at>,
        Christoph Hellwig <hch@infradead.org>, linux-raid@vger.kernel.org,
        xfs@oss.sgi.com, linux-kernel@vger.kernel.org, dm-devel@redhat.com
Subject: Re: direct-io regression [Was: How to track down abysmal
 performance ata - raid1 - crypto - vg/lv - xfs]
Message-ID: <20100805163519.GA6604@comet.dominikbrodowski.net>
Mail-Followup-To: Dominik Brodowski <linux@dominikbrodowski.net>,
	Chris Mason <chris.mason@oracle.com>, josef@redhat.com,
	Valdis.Kletnieks@vt.edu,
	Michael Monnerie <michael.monnerie@is.it-management.at>,
	Christoph Hellwig <hch@infradead.org>, linux-raid@vger.kernel.org,
	xfs@oss.sgi.com, linux-kernel@vger.kernel.org, dm-devel@redhat.com
References: <20100805123649.GA18672@dhcp231-156.rdu.redhat.com>
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 <20100805153519.GA7242@comet.dominikbrodowski.net>
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Small correction:

On Thu, Aug 05, 2010 at 05:35:19PM +0200, Dominik Brodowski wrote:
> With this fix, I get proper speeds when doing dio reads from
> /dev/mapper/vg0-*_crypt; see the 17.3 MB/s above. Most strangely,
> also accesing /dev/mapper/vg0-* (un-encrypted) and the raw
> device at /dev/sda* speeds up (to up to 28 MB/s). Was only seeing around
> 16 to 18 MB/s without this patch for unencrypted access.

The speed-up of the unencrypted access (18 -> 28 MB/s) is caused by using a
different configuration for kernel 2.6.35; and seems to be unrelated to your
patch. Will try to track down which config option is the culprit.


kernel, dmcrypt?	| good config | bad config
-------------------------------------------------
patched 2.6.35, dmcrypt	  ~ 18 MB/s	~ 13 MB/s
patched 2.6.35		  ~ 28 MB/s	~ 18 MB/s
-------------------------------------------------
plain 2.6.35, dmcrypt	  ~  3 MB/s	~  3 MB/s
plain 2.6.35		  <not tested>	~ 16 MB/s	


Best,
	Dominik
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