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Date: Sun, 17 May 2009 08:14:50 -0500
From: "Michael S. Zick" <lkml@...ethan.org>
To: Wu Fengguang <fengguang.wu@...el.com>
Cc: linux-kernel <linux-kernel@...r.kernel.org>,
Christoph Lameter <cl@...ux-foundation.org>,
Ray Lee <ray-lk@...rabbit.org>, Rik van Riel <riel@...hat.com>,
Satish Eerpini <eerpini@...il.com>
Subject: Re: unresponsiveness on linux desktop during file copy
On Sat May 16 2009, you wrote:
> On Sun, May 17, 2009 at 12:30:28PM +0800, Satish Eerpini wrote:
> > > I've prepared a rolled up patch for you, run time tested. It should
> > > protect all of the above pages from being evicted by large file copies.
> > >
> > > The attached patch is for 2.6.29.
> >
> > I applied the patch , but the number don seem to show much difference
>
> The numbers listed in your email? No the most relevant numbers are
> memory and disk ones.
>
> For my part, the number of mapped pages keeps stable when there is an
> ongoing background file copy:
>
> % ls -l /b/sparse
> -rw-r--r-- 1 root root 98T 2009-04-29 22:38 /b/sparse
> % cp /b/sparse /dev/null&
> % for i in `seq 1 100`; do grep Mapped /proc/meminfo; sleep 1; done
> Mapped: 22764 kB
> Mapped: 22796 kB
> Mapped: 22756 kB
> Mapped: 22716 kB
> Mapped: 22800 kB
> Mapped: 22788 kB
> Mapped: 22804 kB
> Mapped: 22808 kB
> Mapped: 22748 kB
> Mapped: 22708 kB
> Mapped: 22916 kB
> Mapped: 22944 kB
> Mapped: 22944 kB
> Mapped: 22944 kB
> Mapped: 22944 kB
> Mapped: 22944 kB
> Mapped: 22832 kB
> Mapped: 22812 kB
> Mapped: 22812 kB
> Mapped: 22792 kB
> Mapped: 22772 kB
> Mapped: 22860 kB
> Mapped: 22860 kB
> Mapped: 22748 kB
> Mapped: 22808 kB
> Mapped: 22868 kB
> Mapped: 22956 kB
> Mapped: 22956 kB
> Mapped: 22832 kB
> Mapped: 22832 kB
> Mapped: 22980 kB
> Mapped: 22980 kB
> Mapped: 22980 kB
> Mapped: 22980 kB
> Mapped: 22872 kB
> Mapped: 22872 kB
> Mapped: 22900 kB
> Mapped: 22792 kB
> Mapped: 22920 kB
> Mapped: 22812 kB
> Mapped: 22812 kB
> Mapped: 22752 kB
> Mapped: 22864 kB
> Mapped: 22972 kB
> Mapped: 22860 kB
> Mapped: 22796 kB
> Mapped: 22900 kB
> Mapped: 22888 kB
> Mapped: 22888 kB
> Mapped: 22888 kB
> Mapped: 22764 kB
>
> > , following are the statistics with the patched kernel, could
> > something else be causing the huge iowait, :
> >
> > Linux 2.6.29 (satish) 05/17/2009
> >
> > 09:57:14 AM CPU %user %nice %system %iowait %steal %idle
> > 09:57:18 AM all 12.93 0.00 10.25 33.44 0.00 43.38
> > 09:57:21 AM all 13.32 0.00 28.09 24.40 0.00 34.19
> > 09:57:24 AM all 10.79 0.00 4.76 75.56 0.00 8.89
> > 09:57:26 AM all 11.46 0.00 8.01 35.64 0.00 44.90
> > 09:57:30 AM all 11.68 0.00 8.88 35.05 0.00 44.39
> > Average: all 12.03 0.00 11.94 40.81 0.00 35.22
>
> The iowait is high. Do you have "iostat -x 5' numbers?
>
> > and
> >
> > hdparm -tT /dev/sda
> >
> > /dev/sda:
> > Timing cached reads: 1332 MB in 2.00 seconds = 666.35 MB/sec
> > Timing buffered disk reads: 24 MB in 3.32 seconds = 7.23 MB/sec
>
> That's pretty slow numbers. On my laptop:
>
> # hdparm -tT /dev/sda
>
> /dev/sda:
> Timing cached reads: 10266 MB in 1.98 seconds = 5188.46 MB/sec
> Timing buffered disk reads: 138 MB in 3.01 seconds = 45.90 MB/sec
>
I see (on 2.6.30-rc6, no patches):
# hdparm -tT /dev/sda (The internal, low-power, low performance hdd):
/dev/sda:
Timing cached reads: 492 MB in 2.00 seconds = 245.83 MB/sec
Timing buffered disk reads: 74 MB in 3.05 seconds = 24.26 MB/sec
# hdparm -tT /dev/sdb (A Class-6, SDHC card):
/dev/sdb:
Timing cached reads: 472 MB in 2.01 seconds = 235.28 MB/sec
Timing buffered disk reads: 40 MB in 3.13 seconds = 12.79 MB/sec
And the only thing going on -
(once you deduct the effect of getting this output) - nothing:
top - 08:09:25 up 9 min, 1 user, load average: 0.24, 0.40, 0.25
Tasks: 86 total, 1 running, 85 sleeping, 0 stopped, 0 zombie
Cpu(s): 2.9%us, 4.2%sy, 0.8%ni, 59.9%id, 32.2%wa, 0.0%hi, 0.1%si, 0.0%st
Mem: 447040k total, 242996k used, 204044k free, 73516k buffers
Swap: 2199324k total, 0k used, 2199324k free, 79868k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
3359 root 20 0 2444 1048 824 R 3.8 0.2 0:00.04 top
3360 root 20 0 3376 888 744 S 1.9 0.2 0:00.01 less
1 root 20 0 3084 1884 564 S 0.0 0.4 0:01.59 init
2 root 15 -5 0 0 0 S 0.0 0.0 0:00.00 kthreadd
Mike
> Thanks,
> Fengguang
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