Re: Page cache write performance issue

[Andrew Morton <akpm@xxxxxxxx>]

Nathan Scott <nathans@xxxxxxx> wrote:
>
> On Wed, Oct 13, 2004 at 01:39:41AM -0700, Andrew Morton wrote:
>  > Nick Piggin <piggin@xxxxxxxxxxxxxxx> wrote:
>  > >
>  > >  Andrew probably has better ideas.
>  > 
>  > uh, is this an ia32 highmem box?
> 
>  Yep, it is.
> 
>  > If so, you've hit the VM sour spot.
>  > ...
>  > Basically, *any* other config is fine.  896MB and below, 1.5GB and above.
> 
>  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.

Can you exhibit this one more than one machine?

Silly question: what does `grep sync' /etc/fstab say over there? ;)