Date: Wed, 13 Jun 2012 08:53:13 +0200
From: Jan Kara <jack@suse.cz>
To: Wallak <wallak@free.fr>
Cc: Jan Kara <jack@suse.cz>, linux-kernel@vger.kernel.org
Subject: Re: File copy is very slow on linux-3.4.2 (or linux-3.3x) on a
 specific hardware: AMD FX-8150 + 990FX
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On Wed 13-06-12 00:41:25, Wallak wrote:
> Jan Kara wrote:
> >On Tue 12-06-12 20:39:32, Wallak wrote:
> >>Jan Kara wrote:
> >>>On Mon 11-06-12 21:54:16, wallak@free.fr wrote:
> >>>>I've a very annoying issue on recent kernel (linux-3.4.2-SMP) with my main motherboard (AMD FX-8150 + 990FX - 8 cores 4.1GHz), file copy is very slow (see below). The same kernel works flawlessly on an AMD E450 2 cores motherboard.
> >>>>
> >>>>Linux-3.2.20 works properly on this hardware.
> >>>>hdparm -t gives good results on both kernels.
> >>>>
> >>>>I've no idea where this bug come from. Do you have this issue on your hardware ? A patch is available ?
> >>>>
> >>>>
> >>>>*linux-3.4.2
> >>>>dd if=../in/file_8gb.tmp of=tmp.tmp bs=1024k count=100
> >>>>100+0 records in
> >>>>100+0 records out
> >>>>104857600 bytes (105 MB) copied, 132.884 s, 789 kB/s
> >>>>
> >>>>
> >>>>*linux-3.2.20
> >>>>dd if=../in/file_8gb.tmp of=tmp.tmp bs=1024k count=100
> >>>>100+0 records in
> >>>>100+0 records out
> >>>>104857600 bytes (105 MB) copied, 3.30793 s, 31.7 MB/s
> >>>   So let's separate reading and writing part first. What is the speed of
> >>>dd if=../in/file_8gb.tmp of=/dev/null bs=1M count=100
> >>>   on both kernels?
> >>>And what is the speed of:
> >>>dd if=/dev/zero of=tmp.tm bs=1M count=100
> >>You're right, the issue is only while writing. The results are below:
> >>
> >>#linux-3.4.2
> >>dd if=/dev/zero of=tmp.tm bs=1M count=100
> >>100+0 records in
> >>100+0 records out
> >>104857600 bytes (105 MB) copied, 151.347 s, 693 kB/s
> >>dd if=../in/file_8gb.tmp of=/dev/null bs=1M count=100
> >>100+0 records in
> >>100+0 records out
> >>104857600 bytes (105 MB) copied, 1.26228 s, 83.1 MB/s
> >>
> >>#linux-3.2.20
> >>dd if=/dev/zero of=tmp.tm bs=1M count=100
> >>100+0 records in
> >>100+0 records out
> >>104857600 bytes (105 MB) copied, 1.00838 s, 104 MB/s
> >>dd if=../in/file_8gb.tmp of=/dev/null bs=1M count=100
> >>100+0 records in
> >>100+0 records out
> >>104857600 bytes (105 MB) copied, 1.26947 s, 82.6 MB/s
> >>
> >>
> >>>   Also what filesystems are you using?
> >>This is an ext2 file system:
> >>
> >>/dev/sda6      ext2    464463364 323380956 141082408  70% /backup
> >   OK, I'm surprised by one thing - how come the writes do no end up cached
> >in memory (thus you should get much higher throughput). Is the filesystem
> >mounted with -o sync option by any chance?
> >
> >								Honza
> 
>     I've tried with an nfs mounted drive, the issue is still there,
> it seems to be global. With sync enabled, the output is quite
> faster, that's quite unexpected.
> On my AMD E450 motherboard this kernel works fine - Are you able to
> reproduce this behavior ?
> 
> 
> #/dev/sda6 /backup ext2 rw,relatime,errors=continue 0 0
> (/proc/mount)
> 100+0 records in
> 100+0 records out
> 104857600 bytes (105 MB) copied, 155.407 s, 675 kB/s
> 
> #/dev/sda6 /backup ext2 rw,sync,relatime,errors=continue 0 0
> 100+0 records in
> 100+0 records out
> 104857600 bytes (105 MB) copied, 69.7868 s, 1.5 MB/s
> 
> #nfs drive - same issue:
> 100+0 records in
> 100+0 records out
> 104857600 bytes (105 MB) copied, 221.572 s, 473 kB/s
  That's really curious. I have not seen your issue although I use current
kernels for development & testing a lot. Also if it was some generic issue
with 3.4 I'm pretty sure we would have heard *much* more complaints from
other users as well. So I think it must be something specific to your setup
/ kernel config.

Can you run:
while true; do
  cat /proc/vmstat
  echo "---"
  cat /proc/meminfo
  echo "------------------"
  sleep 5
done >/tmp/vmstat.out

while the dd is running and send the output please? Also does the problem
go away if you run a 64-bit kernel on the machine?

								Honza
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR
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