slow directory listing

slow directory listing

[Ron Peterson]

I'm setting up a new mail server, and am testing/tweaking IO.  I have
two directories: /test/a which contains 750 mbox files totalling 8GB,
and /test/a2, which contains the exact same number of files, same names,
all zero length.

I am using ext3.  I have done this experiment with both indexed and
non-indexed directories (mke2fs -O dir_index ...).  I have also tried
setting the noatime mount option.

The times taken to do a directory listing are significantly different.

1037# time ls /test/a2 > /dev/null

real    0m0.006s
user    0m0.000s
sys     0m0.006s

1038# time ls /test/a > /dev/null

real    0m5.244s
user    0m4.875s
sys     0m0.346s

If I refer to a specific file, there's still a difference, but only 5x,
vs. 875x above.

1044# time ls a/anmbox > /dev/null

real    0m0.010s
user    0m0.009s
sys     0m0.002s

Fri Jun 10 10:31:02 root@slush:/db/tmp
1045# time ls a2/anmbox > /dev/null

real    0m0.002s
user    0m0.001s
sys     0m0.001s

I'm assuming this is normal behaviour.  (?)  However, I'd like to
understand what's happening a little better, and I'm wondering if
there's anything I'm overlooking vis-a-vis tuning my filesystem properly
for this type of application.

Linux 2.6.11.11 on Debian Sarge.  Dell 2800 w/ LSI Megaraid on PCI/E to
Utra320 SCSI disks.

-- 
Ron Peterson
Network & Systems Manager
Mount Holyoke College
http://www.mtholyoke.edu/~rpeterso

Re: slow directory listing

[Ron Peterson]

On Fri, Jun 10, 2005 at 10:37:20AM -0400, rpeterso wrote:

> I'm setting up a new mail server, and am testing/tweaking IO.  I have
> two directories: /test/a which contains 750 mbox files totalling 8GB,
> and /test/a2, which contains the exact same number of files, same names,
> all zero length.
> ...
> The times taken to do a directory listing are significantly different.

I've become more confused, if that's possible.  I was just editing some
test script in emacs.  As part of the script creation process I used the
M-! command to pipe the output of 'ls /test/a' into a buffer.  It
snapped back almost instantly.

So this seems to have something to do w/ bash, not filesystems.  I
think.  So seems OT for this list, but I still don't understand where
the sluggishness comes from.

BTW, I just did the same test w/ XFS and the results were almost
identical.

Best.

-- 
Ron Peterson
Network & Systems Manager
Mount Holyoke College
http://www.mtholyoke.edu/~rpeterso

Re: slow directory listing

[Bodo Eggert]

Ron Peterson <rpeterso@mtholyoke.edu> wrote:
> On Fri, Jun 10, 2005 at 10:37:20AM -0400, rpeterso wrote:

>> I'm setting up a new mail server, and am testing/tweaking IO.  I have
>> two directories: /test/a which contains 750 mbox files totalling 8GB,
>> and /test/a2, which contains the exact same number of files, same names,
>> all zero length.
>> ...
>> The times taken to do a directory listing are significantly different.
> 
> I've become more confused, if that's possible.  I was just editing some
> test script in emacs.  As part of the script creation process I used the
> M-! command to pipe the output of 'ls /test/a' into a buffer.  It
> snapped back almost instantly.

Try ls|cat and take a look at $LS_OPTIONS and $LS_COLORS. I suspect your
ls tries to use some magic on the files to determine the color.
-- 
Ich danke GMX dafür, die Verwendung meiner Adressen mittels per SPF
verbreiteten Lügen zu sabotieren.

Re: slow directory listing

[David Weinehall]

On Fri, Jun 10, 2005 at 10:37:20AM -0400, Ron Peterson wrote:
[snip]
> The times taken to do a directory listing are significantly different.
> 
> 1037# time ls /test/a2 > /dev/null

[snip]

Do you get the same results if you use ls with the -U (unsorted) flag?


Regards: David Weinehall
-- 
 /) David Weinehall <tao@acc.umu.se> /) Northern lights wander      (\
//  Maintainer of the v2.0 kernel   //  Dance across the winter sky //
\)  http://www.acc.umu.se/~tao/    (/   Full colour fire           (/

Re: slow directory listing

[Ron Peterson]

On Sat, Jun 11, 2005 at 12:12:52AM +0200, Bodo Eggert wrote:
> Ron Peterson <rpeterso@mtholyoke.edu> wrote:
> > On Fri, Jun 10, 2005 at 10:37:20AM -0400, rpeterso wrote:
> 
> >> I'm setting up a new mail server, and am testing/tweaking IO.  I have
> >> two directories: /test/a which contains 750 mbox files totalling 8GB,
> >> and /test/a2, which contains the exact same number of files, same names,
> >> all zero length.
> >> ...
> >> The times taken to do a directory listing are significantly different.
> > 
> > I've become more confused, if that's possible.  I was just editing some
> > test script in emacs.  As part of the script creation process I used the
> > M-! command to pipe the output of 'ls /test/a' into a buffer.  It
> > snapped back almost instantly.
> 
> Try ls|cat and take a look at $LS_OPTIONS and $LS_COLORS. I suspect your
> ls tries to use some magic on the files to determine the color.

ls was aliased to 'ls -F', it just took me a while to notice...

-- 
Ron Peterson
Network & Systems Manager
Mount Holyoke College
http://www.mtholyoke.edu/~rpeterso

Re: slow directory listing

[Vladimir Saveliev]

Hello

On Mon, 2005-06-13 at 16:05, Ron Peterson wrote:
> On Sat, Jun 11, 2005 at 12:12:52AM +0200, Bodo Eggert wrote:
> > Ron Peterson <rpeterso@mtholyoke.edu> wrote:
> > > On Fri, Jun 10, 2005 at 10:37:20AM -0400, rpeterso wrote:
> > 
> > >> I'm setting up a new mail server, and am testing/tweaking IO.  I have
> > >> two directories: /test/a which contains 750 mbox files totalling 8GB,
> > >> and /test/a2, which contains the exact same number of files, same names,
> > >> all zero length.
> > >> ...
> > >> The times taken to do a directory listing are significantly different.
> > > 

Which filesystem is used for /test?

> > > I've become more confused, if that's possible.  I was just editing some
> > > test script in emacs.  As part of the script creation process I used the
> > > M-! command to pipe the output of 'ls /test/a' into a buffer.  It
> > > snapped back almost instantly.
> > 
> > Try ls|cat and take a look at $LS_OPTIONS and $LS_COLORS. I suspect your
> > ls tries to use some magic on the files to determine the color.
> 
> ls was aliased to 'ls -F', it just took me a while to notice...