On Sun, Jul 22, 2012 at 11:47:57PM +0200, Arno Wagner wrote:
> On Sun, Jul 22, 2012 at 01:39:29PM -0700, Marc MERLIN wrote:
> > On Sun, Jul 22, 2012 at 09:47:32PM +0200, Yves-Alexis Perez wrote:
> > > > Any suggestions would be appreciated.
> > >
> > > I'm using Debian sid (so still at 3.2 kernel), currently using a 256G
> > > Samsung SSD. What I get is:
>
> SID? That would be "unstable", whit possible assorted problems.
>
> [...]
> > gandalfthegreat:~# dd if=/dev/mapper/ssdcrypt of=/dev/null bs=1M count=1024
> > 1073741824 bytes (1.1 GB) copied, 44.3302 s, 24.2 MB/s
> >
> > atop shows dd isn't really pegging a single core:
> > THR SYSCPU USRCPU RDDSK WRDSK ST EXC S CPUNR CPU CMD
> > 1 0.60s 0.01s 226.2M 0K -- - D 3 6% dd
>
> It would not, as AES-NI (AFAIK) does need very little CPU
> assistance. AES-NI may be the problem though. Can you try with
> the normal AES module? I think unloading the AES-NI module
> may be enough for that, but I am not sure.
>
> Maybe AES-NI needs very long for something it needs to do each
> sector. Google("aes-ni slow") found at least some indications that
> aes-ni may still have problems.
It was worth a shot, thanks for the suggestion.
gandalfthegreat:~# lsmod | grep aes
aes_x86_64 16796 34
gandalfthegreat:~# hdparm -t -T /dev/mapper/cryptroot
/dev/mapper/cryptroot:
Timing cached reads: 15802 MB in 2.00 seconds = 7909.98 MB/sec
Timing buffered disk reads: 68 MB in 3.04 seconds = 22.39 MB/sec
gandalfthegreat:~#
Unfortunately, speed is exactly the same.
with aes_x86_64:
gandalfthegreat:/var/local/VirtualBox VMs/w2k_virtual# dd if=test of=/dev/null
4192640+0 records in
4192640+0 records out
2146631680 bytes (2.1 GB) copied, 12.4848 s, 172 MB/s
I then rebooted with aesni_intel and got this:
gandalfthegreat:/var/local/VirtualBox VMs/w2k_virtual# dd if=test of=/dev/null
4192640+0 records in
4192640+0 records out
2146631680 bytes (2.1 GB) copied, 8.42506 s, 255 MB/s
So those speeds are expected/believable, but I still don't know why
hdparm is so slow on /dev/mapper/cryptroot.
Mmmh....
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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