Re: Page cache write performance issue

[Nick Piggin <nickpiggin@xxxxxxxxxxxx>]

Nathan Scott wrote:
> On Wed, Oct 13, 2004 at 08:20:41PM -0700, Andrew Morton wrote:
>
> > Nathan Scott <nathans@xxxxxxx> wrote:
> >
> > > I just tried switching CONFIG_HIGHMEM off, and so running the
> > > machine with 512MB; then adjusted the test to write 256M into
> > > the page cache, again in 1K sequential chunks.  A similar mis-
> > > behaviour happens, though the numbers are slightly better (up
> > > from ~4 to ~6.5MB/sec).  Both ext2 and xfs see this.  When I
> > > drop the file size down to 128M with this kernel, I see good
> > > results again (as we'd expect).
> > No such problem here, with
> >
> >         dd if=/dev/zero of=x bs=1k count=128k
> >
> > on a 256MB machine.  xfs and ext2.
>
> Yup, rebooted with mem=128M and on my box, & that crawls.
> Maybe its just this old hunk 'o junk, I suppose; odd that
> 2.6.8 was OK with this though.
Just out of interest, can you get profiles and a few lines
of vmstat 1 from 2.6.8 and 2.6.9-rc, please?