On Tue, Jul 24, 2012 at 04:58:17PM +0200, Heinz Diehl wrote:
> 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
Funny you'd say that. I checked mine (with 3.4.4)
By default, it comes with:
gandalfthegreat:~# blockdev --report /dev/sda2
RO RA SSZ BSZ StartSec Size Device
rw 256 512 4096 502272 26843283456 /dev/sda2
gandalfthegreat:~# blockdev --setra 0 /dev/sda2
gandalfthegreat:~# hdparm -t /dev/sda2
/dev/sda2:
Timing buffered disk reads: 2 MB in 4.81 seconds = 425.77 kB/sec
gandalfthegreat:~# hdparm --direct -t /dev/sda2
/dev/sda2:
Timing O_DIRECT disk reads: 432 MB in 3.01 seconds = 143.68 MB/sec
So I know it doens't make sense, but apparently it's SSD/machine sensitive
and for me the default of 256 is enough for the block device, but not enough
for a dm-crypt'ed device.
I just checked that my other dmcrypt device I just created:
gandalfthegreat:~# blockdev --report /dev/mapper/test
RO RA SSZ BSZ StartSec Size Device
rw 256 512 4096 0 26839089152 /dev/mapper/test
So I do get 256 RA consistently and it's enough for the raw block device,
but not enough for a dm-crypted device.
gandalfthegreat:~# hdparm -t /dev/mapper/test
/dev/mapper/test:
Timing buffered disk reads: 66 MB in 3.05 seconds = 21.62 MB/sec
By the way, just for run, I tried
cryptsetup luksFormat --align-payload=8192 -c twofish-xts-plain64 /dev/sda2
instead of
cryptsetup luksFormat --align-payload=8192 -c aes-xts-plain /dev/sda2
since it was suggested that it might be faster on recent laptops.
Well, on a Lenovo 530 with
model name : Intel(R) Core(TM) i7-3520M CPU @ 2.90GHz
I get 177 MB/s for twofish-xts-plain64 and 281 MB/s for aes-xts-plain
For comparison, I got 406 MB/s for null dmcrypt.
So it sounds like for my SSD, aes-xts-plain is the fastest with aesni_intel
once I've run blockdev --settra 8192.
I tried --settra 81920 (10x more) and it raised aes-xts-plain from 281MB/s
to 298MB/s and null dmcrypt 406MB/s to 446MB/s.
Hope this helps.
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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