Re: journaling & VM

[Hans Reiser <hans@reiser.to>]

"Stephen C. Tweedie" wrote:
> 
> Hi,
> 
> On Wed, Jun 07, 2000 at 02:29:25PM -0700, Hans Reiser wrote:
> >
> > If I understand Juan correctly, they fixed this issue.  Aging 1/64th of the
> > cache for every cache evenly at every round of trying to free pages should be an
> > excellent fix.  It should do just fine at the task of handling a system with
> > both ext3 and reiserfs running.
> 
> That is _exactly_ what breaks the VM balance!  The net result of
> an algorithm like that is that all caches are shrunk at the same
> rate regardless of which ones are busy.  The "shrink everything
> at once" principle is what used to cause large filesystem scans
> (such as find|grep over a large source tree) to swap all our
> running processes out.
> 
> There _has_ to be a way to allow the relative ages of the different
> pages to influence the reclamation of pages from different sources.
> 
> Cheers,
>  Stephen

I am confused, if a page is accessed the aging is undone.  Aging 1/64th is not
the same as flushing 1/64th.  If cache A is not used the aging process gradually
shrinks it to nothing because its pages aren't unaged, if cache B is heavily
used the aging process doesn't age fast enough to overcome the unaging and new
pages get added and it grows.  I am missing something....

Hans
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