[dm-crypt] aes-xts-plain with aes_x86_64 makes my SSD 5x slower than my encrypted HD

Marc MERLIN marc at merlins.org
Tue Jul 24 18:09:10 CEST 2012


On Tue, Jul 24, 2012 at 05:19:26PM +0200, Milan Broz wrote:
> I have no time to check it today but this must be fixed. Read-ahead
> is just stupid workaround...
> 
> # echo "0">/sys/block/sdc/queue/rotational 
> # hdparm -t /dev/mapper/sdc_null_crypt 
>  Timing buffered disk reads:  220 MB in  3.01 seconds =  73.07 MB/sec
> 
> # echo "1">/sys/block/sdc/queue/rotational 
> # hdparm -t /dev/mapper/sdc_null_crypt 
>  Timing buffered disk reads:  652 MB in  3.01 seconds = 216.75 MB/sec
> 
> This SSD is quicker if set to rotational mode!
> (So it merges requests in fact.)

That didn't help for me, strangely.

gandalfthegreat:~# blockdev --setra 256 /dev/mapper/cryptroot 
gandalfthegreat:~# reset_cache 
gandalfthegreat:~# dd if=/dev/mapper/cryptroot of=/dev/null bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 43.4968 s, 24.7 MB/s
gandalfthegreat:~# dmsetup ls | grep cryptroot
cryptroot	(254:0)
gandalfthegreat:~# echo "1">/sys/block/dm-0/queue/rotational
gandalfthegreat:~# reset_cache 
gandalfthegreat:~# dd if=/dev/mapper/cryptroot of=/dev/null bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 42.9933 s, 25.0 MB/s

Marc
-- 
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems ....
                                      .... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/  


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