On Wed, 6 Nov 2013 15:43:02 +0900 Minchan Kim <minchan@xxxxxxxxxx> wrote: > > The added overhead is pretty small - just a comparison of a local with > > a constant. And that cost is not incurred for MIGRATE_UNMOVABLE, > > MIGRATE_RECLAIMABLE and MIGRATE_MOVABLE, which are the common cases > > (yes?). > > True but bloat code might affect icache so we should be careful. > And what Mel has a concern is about zone->lock, which would be more contended. > I agree his opinion. > > In addition, I think the gain is marginal because normally CMA is big range > so free_contig_range in dma release path will fill per_cpu_pages with freed pages > easily so it could drain per_cpu_pages frequently so race which steal page from > per_cpu_pages is not big, I guess. > > Morever, we could change free_contig_range with batch_free_page which would > be useful for other cases if they want to free many number of pages > all at once. > > The bottom line is we need *number and real scenario* for that. Well yes, quantitative results are always good to have with a patch like this. It doesn't actually compile (missing a "}"), which doesn't inspire confidence. I'll make the patch go away for now -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>