Extreme slowness with xfs [WAS: Re: Slowness with new pc]

[Michael Tokarev]

Justin Piszcz wrote:
[]
> barriers enabled:
> real    2m40.643s
> barriers disabled:
> real    0m27.612s

Barriers enabled:

$ time sh -c "tar xf linux-2.6.27.tar.bz2; sync"
real	2m3.317s
user	0m33.990s
sys	0m3.980s

$ time sh -c "rm -rf linux-2.6.27; sync"
real	1m4.033s
user	0m0.080s
sys	0m2.860s


Barriers disabled:

$ time sh -c "tar xf linux-2.6.27.tar.bz2; sync"
real	0m36.279s
user	0m25.610s
sys	0m2.800s

$ time sh -c "rm -rf linux-2.6.27; sync"
real	0m3.694s
user	0m0.010s
sys	0m2.230s


During unpack, with barriers=on, the cpu usage stays
hardy noticeable, while with barriers=off, the thing
becomes CPU-bound (needed for bzip2).

For comparison, here are results for jfs on the
same drive:

$ time sh -c "tar xf /stage/build/kernel/linux-2.6.27.tar.bz2; sync"
real	0m36.062s
user	0m25.370s
sys	0m2.860s

$ time sh -c "rm -rf linux-2.6.27; sync"
real	0m3.024s
user	0m0.040s
sys	0m0.750s

This jfs partition is located a bit further on the same disk,
so raw speed of it is a bit lower.  Yet the numbers are pretty
similar.  In any case, xfs with barriers is MUCH worse...

The disk is a 500Gig Hitachi HUA72105 one ("raid edition"),
on an AMD 780g/SB700 chipset in ahci mode.

/mjt