Re: Page cache write performance issue

[Nathan Scott]

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).

I'm being pulled onto other issues atm, but in the background
I could try reverting specific changesets if you guys can
suggest anything in particular that might be triggering this?

thanks!

-- 
Nathan
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