Re: 2.4 fix for write throttling on x86 >1G

Marcelo Tosatti
2005-03-11T21:19:28Z

On Fri, Mar 11, 2005 at 09:53:09PM +0100, Andrea Arcangeli wrote:
> Hello Marcelo,
>
> On Fri, Mar 11, 2005 at 01:04:13PM -0300, Marcelo Tosatti wrote:
> > Out of curiosity, that was SuSE not mainline ?
>
> yep.
>
> > Do we really want to limit dirty cache to low mem on HIGHIO capable
> > machines? I'm afraid doing so might hurt performance on such systems.
> >
> > I think it might be wise to have nr_free_buffer_pages() take highmem
> > into account if CONFIG_HIGHIO is set ?
>
> The problem is the buffercache/blkdev-pagecache: it simply can't go in
> highmem. A similar fix happened recently in 2.6 for the same reasons,
> but in 2.6 we allowed it with some logic specific for the
> blkdev-pagecache.

Right, I dont think it is easy nor wanted to make that distiction in v2.4.

> nr_free_buffer_pages() was never intended to take highmem into account,
> that's why there's the GFP_USER thing already, except we didn't loop
> into the zonelist, so I didn't try to make a fix similar to 2.6.

Hopefully it is not a big deal to not-allow >1GB dirty pagecache on v2.4.

Applied, thanks.