Re: [patch][rfc][rft] vm throughput 2.4.2-ac4

Marcelo Tosatti
2001-03-07T00:08:09Z

On Fri, 2 Mar 2001, Mike Galbraith wrote:

> On Thu, 1 Mar 2001, Rik van Riel wrote:
>
> > > > The merging at the elevator level only works if the requests sent to
> > > > it are right next to each other on disk. This means that randomly
> > > > sending stuff to disk really DOES DESTROY PERFORMANCE and there's
> > > > nothing the elevator could ever hope to do about that.
> > >
> > > True to some (very real) extent because of the limited buffering
> > > of requests. However, I can not find any useful information
> > > that the vm is using to guarantee the IT does not destroy
> > > performance by your own definition.
> >
> > Indeed. IMHO we should fix this by putting explicit IO
> > clustering in the ->writepage() functions.
>
> I notice there's a patch sitting in my mailbox.. think I'll go read
> it and think (grunt grunt;) about this issue some more.

Mike,

One important information which is not being considered by
page_launder() now the dirty buffers watermark.

In general, it should not try to avoid writing dirty pages if we're above
the dirty buffers watermark.