Re: [PATCH]: Clean up of __alloc_pages

Rohit Seth
2005-10-03T16:48:54Z

On Mon, 2005-10-03 at 08:34 -0700, Christoph Lameter wrote:
> On Sat, 1 Oct 2005, Seth, Rohit wrote:
>
> > - goto zone_reclaim_retry;
> > - }
> > + if (order == 0) {
> > + for (i = 0; (z = zones[i]) != NULL; i++) {
> > + page = buffered_rmqueue(z, 0, gfp_mask, 0);
> > + if (page)
> > + goto got_pg;
> > }
> > -
>
> This is checking all zones for pages on the pcp before going the more
> expensive route?
>

That is right.

> Seems that this removes the logic intended to prefer local
> allocations over remote pages present in the existing alloc_pages? There
> is the danger that this modification will lead to the allocation of remote
> pages even if local pages are available. Thus reducing performance.
>

Good catch. I will up level the cpuset check in buffered_rmqueue rather
then doing it in get_page_from_freelist. That should retain the current
preferences for local pages.

> I would suggest to just check the first zone's pcp instead of all zones.
>

Na. This for most cases will be ZONE_DMA pcp list having nothing much
most of the time. And picking any other zone randomly will be exposed
to faulty behavior.

Thanks,
-rohit