Re: Drastic performance issue in ext2 v ffs

Steven N. Hirsch (shirsch@adelphia.net)
Wed, 6 Jan 1999 07:45:37 -0500 (EST)


On Tue, 5 Jan 1999, Tom Christiansen wrote:

> I believe there is something dramatically wrong here, probably in either
> the ext2 filesystems or the SCSI driver, or both. Here's the story.
>
> I have two boxes. One is a Pentium-Pro (200 Mhz) running a Linux 2.0.36
> kernel under Redhat 5.2. The other is a Pentium-II (300 Mhz) running
> OpenBSD 2.4. Both have 128M memory and large SCSI disks. Linux is
> using ext2 filesystems, and BSD ffs filesystems.
>
> The deal is that I ran recursive directory operations on duplicate
> directories (about 55meg) on each machine, and no matter what I did,
> the Linux times were more than an order of magnitude worse. I can't
> account for that, and I'd like to.
>
> My first test was du on that directory tree. Here are the timing results
> of "du -s >/dev/null".
>
> linux 0.080u 11.400s 0:11.51
> bsd 0.030u 0.462s 0:00.49
>
> That I found remarkable. So I tried find.
> Here are timings on "find . -ls >/dev/null":
>
> linux 1.050u 12.130s 0:13.35
> bsd 0.739u 0.445s 0:01.18

As another data-point, running 'find . -ls > /dev/null' against the linux
2.2.0-pre4 source tree (~66meg) gives:

1.05user 0.82system 0:02.02elapsed

'du -s > /dev/null' gives:

0.13user 0.68system 0:00.81elapsed

Both timings were performed on a Pentium 166 machine w/ 64Meg of memory,
Adaptec 2940W controller and Fast/Wide SCSI-2 disk (7200rpm).

This is the desired order-of-magnitude, no?

Steve

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