On Mon, 17 Jun 2002, Andrew Morton wrote:
> dean gaudet wrote:
> > what if you have a disk array with lots of spindles? it seems at some
> > point that you need to give the array or some lower level driver a lot of
> > i/os to choose from so that it can get better parallelism out of the
> > hardware.
>
> mm. For that particular test, you'd get nice speedups from striping
> the blockgroups across disks, so each `cat' is probably talking to
> a different disk. I don't think I've seen anything like that proposed
> though.
heh, a 128MB stripe? that'd be huge :)
> You could fork one `cat' per file ;) (Not so silly, really. But if
> you took this approach, you'd need "many" more threads than blockgroups).
i actually tried this first :) the problem then becomes a fork()
bottleneck before you run into the disk bottlenecks. iirc the numbers
were ~45s for the 1-file-per-cat (for any -Pn, n<=10), ~30s for
100-files-per-cat (-P1) and ~1m15s for 100-files-per-cat (-P2).
> hmm. What else? Physical readahead - read metadata into the block
> device's pagecache and flip pages from there into directories and
> files on-demand. Fat chance of that happening.
one idea i had -- given that the server has a volume manager and you're
working from a snapshot volume anyhow (only sane way to do backups), it
might make a lot more sense to use userland ext2/3 libraries to read the
snapshot block device anyhow. but this kind of makes me cringe :)
-dean
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This archive was generated by hypermail 2b29 : Sun Jun 23 2002 - 22:00:15 EST