Bob Friesenhahn <bfrie...@simple.dallas.tx.us> wrote:
> On Mon, 13 Jul 2009, Mike Gerdts wrote:
> >
> > Using cpio's -C option seems to not change the behavior for this bug,
> > but I did see a performance difference with the case where I hadn't
> > modified the zfs caching behavior. That is, the performance of the
> > tmpfs backed vdisk more than doubled with "cpio -o -C $((1024 * 1024))
> >> /dev/null". At this point cpio was spending roughly 13% usr and 87%
> > sys.
>
> Interesting. I just updated zfs-cache-test.ksh on my web site so that
> it uses 131072 byte blocks. I see a tiny improvement in performance
> from doing this, but I do see a bit less CPU consumption so the CPU
> consumption is essentially zero. The bug remains. It seems best to
> use ZFS's ideal block size so that issues don't get confused.
If you continue to use cpio and the cpio archive format, you force copying a
lot of data as the cpio archive format does use odd header sizes and starts
new files "unaligned" directly after the archive header.
Jörg
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