Re: [2.4.17/18pre] VM and swap - it's really unusable

Stephan von Krawczynski
2002-01-04T14:24:52Z

On Fri, 4 Jan 2002 15:14:38 +0100
Andrea Arcangeli <andrea@suse.de> wrote:

> On Fri, Jan 04, 2002 at 01:33:21PM +0100, Stephan von Krawczynski wrote:
> > On Thu, 03 Jan 2002 20:14:42 -0600
> > "M.H.VanLeeuwen" <vanl@megsinet.net> wrote:
> >
> > And there is another difference here:
> >
> > + if (max_mapped <= 0 && nr_pages > 0)
> > + swap_out(priority, gfp_mask, classzone);
> > +
> >
> > It sounds reasonable _not_ to swap in case of success (nr_pages == 0).
> > To me this looks pretty interesting. Is something like this already in -aa?
> > This patch may be worth applying in 2.4. It is small and looks like the
right> > thing to do.
>
> -aa swapout as soon as max_mapped hits zero. So it basically does it
> internally (i.e. way more times) and so it will most certainly be able
> to sustain an higher swap transfer rate. You can check with the mtest01
> -w test from ltp.

Hm, but do you think this is really good in overall performance, especially the
frequent cases where no swap should be needed _at all_ to do a successful
shrinking? And - as can be viewed in Martins tests - if you have no swap at
all, you seem to trigger OOM earlier through the short path exit in shrink,
which is a obvious nono. I would state it wrong to fix the oom-killer for this
case, because it should not be reached at all.

?

Regards,
Stephan