Hopefully someone will get back to you with a technical explanation,
but the rm times for XFS have always been slow - even under IRIX.
For example, the untar time that you presented is *less than* the
rm time. That is particularly annoying when running an untar at
the same time as an rm of another directory with the hope that disk
won't fill up. Unfortunately, it can fill the disk faster than
it can clean it off, which is a little suprising the first time
you run out of disk space because of this.
XFS does have to log the removes, but it seems like that should be
more like a factor of 2 hit than the factor of 10 that you got
over ext2.
Steve
(Another one interested in the real answer)
On Mar 4, 10:28pm, Vladimir Vukicevic wrote:
> Subject: questions about some benchmarks
>
> Howdy.. I just converted my laptop's root partition to XFS; while
> doing some hacking I ended up doing a quick-and-dirty benchmark
> between XFS and ext2.
>
> The freedb database (www.freedb.org) is a 59MB .tar.bz2 that expands
> out into 1.1GB worth of little files, all 1-2K in size, mostly towards
> the 1K size. (Why they use the filesystem as the database and not use
> libdb or something is beyond me. Anyway.) So, I timed the untar and
> rm -rf times of this tree.
>
> The two machines involved are an IBM X20 laptop, P3-600, 392MB ram,
> 20GB IBM Travelstar 4200 RPM drive, UDMA mode3, xfs filesystem. On my
> desktop, which is an Athlon 700, VIA VT82Cxxx Apollo chipset, 512MB
> ram, tar file on an UATA/100 drive on the primary on-board interface,
> destination drive on a promise UATA/100 IDE controller with an IBM
> Deskstar 7200 RPM 45GB drive on it, with an ext2 filesystem:
>
> On my laptop (xfs),
>
> tar xjf ../freedb-complete-20010219.tar.bz2 138.88s user
> 207.17s system 27% cpu 21:17.84 total
> rm -rf db 1.45s user 130.99s system 9% cpu 24:24.66 total
>
> On my desktop (ext2),
>
> tar xjf ~vladimir/freedb-complete-20010219.tar.bz2 153.76s user
> 2772.26s system 98% cpu 49:28.47 total
> rm -rf db 0.16s user 73.39s system 94% cpu 1:18.24 total
>
> Now, I converted the filesystem on my desktop to XFS. Here's the same
> numbers again, this time for xfs.
>
> tar xjf ~vladimir/freedb-complete-20010219.tar.bz2 156.77s user
> 199.28s system 61% cpu 9:41.88 total
> rm -rf db 1.73s user 131.59s system 19% cpu 11:07.25 total
>
>
> So:
>
> System tar time cpu rm time cpu
> P3-600/4200rpm, xfs 21:17.84 27% 24:24.66 9%
> K7-700/7200rpm, xfs 9:41.88 61% 11:07.25 19%
> K7-700/7200rpm, ext2 49:28.47 98% 1:18.24 94%
>
> So, while xfs obviously kicks ext2's butt, I'm curious as to the cpu
> usage numbers of both the untar and the remove, and also of xfs's
> significantly slower remove times (even though its cpu usage was
> also significantly lower).. is there anything about xfs that
> causes removes to be significantly slower? (I just realized that
> I didn't time a 'sync' after the relevant removes though, so
> a good chunk of this could have even been buffered, maybe...)
>
> I realize that this was an ad-hoc benchmark, but the numbers seemed
> interesting nonetheless. (If anyone's interested in testing the same,
> the database is available at ftp://ftp.freedb.org/pub/freedb/ ).
>
> - Vlad
>-- End of excerpt from Vladimir Vukicevic
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