Re: 2.6.0-test9 - poor swap performance on low end machines

Con Kolivas
2003-10-31T12:38:03Z

On Fri, 31 Oct 2003 22:26, Roger Luethi wrote:
> On Thu, 30 Oct 2003 22:57:23 -0500, Rik van Riel wrote:
> > On Wed, 29 Oct 2003, Chris Vine wrote:
> > > However, on a low end machine (200MHz Pentium MMX uniprocessor with
> > > only 32MB of RAM and 70MB of swap) I get poor performance once
> > > extensive use is made of the swap space.
> >
> > Could you try the patch Con Kolivas posted on the 25th ?
> >
> > Subject: [PATCH] Autoregulate vm swappiness cleanup
>
> I suppose it will show some improvement but fail to get performance
> anywhere near 2.4 -- at least that's what my own tests found. I've been
> working on a break-down of where we're losing it.
> Bottom line: It's not simply a price we pay for feature X or Y. It's
> all over the map, and thus no single patch can possibly fix it.

Yes it will show improvement, and I would like to hear how much given how
simple it is, but I agree with you. There is an intrinsic difference in the
vm in 2.6 that makes it too hard for multiple running applications to have a
small piece of the action instead of giving out big pieces of the action.
While it is better in most circumstances I believe you describe well the
problem under vm overload. I guess encoding a vm scheduler will help (and
clearly 2.8 territory) but at what overhead cost? I have no idea myself, as
now I'm pulling catch-phrases out of my arse that I hate hearing others use
(see any lkml thread about scheduling from people who don't code).

Cheers,
Con