Benchmarking mpsafevfs with parallel tarball extraction

[Kris Kennaway]

On Fri, May 06, 2005 at 11:35:29AM -0700, Kris Kennaway wrote:

> I might be bumping into the bandwidth of md here - when I ran less
> rigorous tests with lower concurrency of extractions I seemed to be
> getting marginally better performance (about an effective concurrency
> of 2.2 for both 3 and 10 simultaneous extractions - so at least it
> doesn't seem to degrade badly).  Or this might be reflecting VFS lock
> contention (which there is certainly a lot of, according to mutex
> profiling traces).

I suspect that I am hitting the md bandwidth:

# dd if=/dev/zero of=/dev/md0 bs=1024k count=500
500+0 records in
500+0 records out
524288000 bytes transferred in 9.501760 secs (55177988 bytes/sec)

which is a lot worse than I expected (even for a 400MHz CPU).

For some reason I get better performance writing to a filesystem
mounted on this md:

# dd if=/dev/zero of=foo bs=1024k count=500
500+0 records in
500+0 records out
524288000 bytes transferred in 7.943042 secs (66005946 bytes/sec)
# rm foo
# dd if=/dev/zero of=foo bs=1024k count=500
500+0 records in
500+0 records out
524288000 bytes transferred in 7.126929 secs (73564364 bytes/sec)
# rm foo
# dd if=/dev/zero of=foo bs=1024k count=500
500+0 records in
500+0 records out
524288000 bytes transferred in 7.237668 secs (72438804 bytes/sec)

If the write bandwidth is only 50-70MB/sec, then it won't be hard to
saturate, so I won't probe the full scalability of mpsafevfs here.

Kris
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