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Date: Tue, 24 Jul 2012 16:58:17 +0200
From: Heinz Diehl <htd@fancy-poultry.org>
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Subject: Re: [dm-crypt] aes-xts-plain with aes_x86_64 makes my SSD 5x slower
 than my encrypted HD
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To: Milan Broz <mbroz@redhat.com>
Cc: dm-crypt@saout.de

On 24.07.2012, Heinz Diehl wrote: 

[....]

And that's obviously not all. The problem occurs also with _unencrypted_
partitions/devices, here's the proof (/dev/sda1 is a 500M ext2
partition mounted on /boot; using the same Hitachi rotational drive as
in my previous test):

[root@wildsau /]# blockdev --setra 8192 /dev/sda1
[root@wildsau /]# hdparm -t /dev/sda1
Timing buffered disk reads: 236 MB in  3.00 seconds =  78.57 MB/sec


[root@wildsau /]# blockdev --setra 0 /dev/sda1
[root@wildsau /]# hdparm -t /dev/sda1
Timing buffered disk reads:  26 MB in  3.05 seconds =   8.51 MB/sec


[root@wildsau /]# blockdev --setra 0 /dev/sda1
[root@wildsau /]# hdparm --direct -t /dev/sda1
Timing O_DIRECT disk reads: 236 MB in  3.02 seconds =  78.09 MB/sec

All this is on F17, with a vanilla 3.5 kernel from kernel.org 
(with just 3 own small patches wich do not touch code involved here).