Re: [2.4] heavy-load under swap space shortage

Andrea Arcangeli
2004-03-16T13:47:17Z

On Tue, Mar 16, 2004 at 03:31:33AM -0300, Marcelo Tosatti wrote:
>
>
> On Sun, 14 Mar 2004, Andrew Morton wrote:
>
> > Andrea Arcangeli <andrea@suse.de> wrote:
> > >
> > > >
> > > > Having a magic knob is a weak solution: the majority of people who are
> > > > affected by this problem won't know to turn it on.
> > >
> > > that's why I turned it _on_ by default in my tree ;)
> >
> > So maybe Marcelo should apply this patch, and also turn it on by default.
>
> Hhhmm, not so easy I guess. What about the added overhead of
> lru_cache_add() for every anonymous page created?
>
> I bet this will cause problems for users which are happy with the current
> behaviour. Wont it?

the lru_cache_add is happening in 2.4 mainline, the only point of the
patch is to _avoid_ calling lru_cache_add (tunable with a sysctl so you
can get to the old behaviour of calling lru_cache_add for every anon
page).

> Andrea, do you have any numbers (or at least estimates) for the added
> overhead of instantly addition of anon pages to the LRU? That would be
> cool to know.

I've the numbers for the removed overhead, that's significant in some
workload, but only in the >=16-ways.

> Obviously we dont have, and dont want to, such things in 2.4.

agreed ;)

> Anyway, it seems this discussion is being productive. Glad!

yep!