On Tue, Jun 19, 2012 at 03:04:59PM +0200, Bartlomiej Zolnierkiewicz wrote:

quoted

If the page is on the wrong free list, just isolate it or move it to the
MIGRATE_ISOLATE free list at that point. If it has been allocated then
migrate it and move the resulting free page to the MIGRATE_ISOLATE list.

Thanks, this makes sense but still leaves us with some page allocation vs
alloc_contig_range() races (i.e. pages "in-flight" state being added/removed
to/from pcp lists so not being on the freelists and not being allocated).

The races should not be forever or open-ended. Once the pageblock is
marked ISOLATE it should only take one pass to either move it from
MIGRATE_CMA to MIGRATE_ISOLATE free lists or to migrate the page and
free it to the MIGRATE_ISOLATE.

I would be very surprised if this cannot be properly handled in
alloc_contig_range() in a manner that does not wreck the page allocator
fast paths.

-- 
Mel Gorman
SUSE Labs

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>