Re: [PATCH] allocate page caches pages in round robin fasion

[Jesse Barnes <jbarnes@engr.sgi.com>]

On Thursday, August 12, 2004 6:14 pm, Andi Kleen wrote:
> Jesse Barnes <jbarnes@engr.sgi.com> writes:
> > On a NUMA machine, page cache pages should be spread out across the
> > system since they're generally global in nature and can eat up whole
> > nodes worth of memory otherwise.  This can end up hurting performance
> > since jobs will have to make off node references for much or all of their
> > non-file data.
> >
> > The patch works by adding an alloc_page_round_robin routine that simply
> > allocates on successive nodes each time its called, based on the value of
> > a per-cpu variable modulo the number of nodes.  The variable is per-cpu
> > to avoid cacheline contention when many cpus try to do page cache
> > allocations at
>
> I don't like this approach using a dynamic counter. I think it would
> be better to add a new function that takes the vma and uses the offset
> into the inode for static interleaving (anonymous memory would still
> use the vma offset). This way you would have a good guarantee that the
> interleaving stays interleaved even when the system swaps pages in and
> out and you're less likely to get anomalies in the page distribution.

Well, that's one reason I didn't add an alloc_pages routine, but just a single 
page distributor.  However, a multipage round robin routine would be useful 
in other cases, like for the slab allocator.

Jesse