Re: ~500 megs cached yet 2.6.5 goes into swap hell

Marc Singer
2004-04-29T04:20:51Z

On Thu, Apr 29, 2004 at 01:48:02PM +1000, Nick Piggin wrote:
> Marc Singer wrote:
> >On Thu, Apr 29, 2004 at 10:21:24AM +1000, Nick Piggin wrote:
> >
> >>Anyway, I have a small set of VM patches which attempt to improve
> >>this sort of behaviour if anyone is brave enough to try them.
> >>Against -mm kernels only I'm afraid (the objrmap work causes some
> >>porting difficulty).
> >
> >
> >Is this the same patch you wanted me to try?
> >
> > Remember, the embedded system where NFS IO was pushing my
> > application out of memory. Setting swappiness to zero was a
> > temporary fix.
> >
> >
>
> Yes this is the same patch I wanted you to try. Yes I
> remember your problem!
>
> Didn't anyone come up with a patch for you to test the
> stale PTE theory? If so, what where the results?

Russell King is working on a lot of things for the MMU code in ARM.
I'm waiting to see where he ends up. I believe he's planning on
removing the lazy PTE release logic.

I hacked at it for some time. And I'm convinced that I correctly
forced the TLBs to be flushed. Still, I was never able to get the
system to behave.

Now, I just read a comment you or WLI made about the page cache
use-once logic. I wonder if that's the real culprit? As I wrote to
Andrew Morton, the kernel seems to be assigning an awful lot of value
to page cache pages that are used once (or twice?). I know that it
would be expensive to perform an HTG aging algorithm where the head of
the LRU list is really LRU. Does your patch pursue this line of
thought?