On Tue, 11 Sep 2012 09:41:52 +0900 Minchan Kim <minchan@xxxxxxxxxx> wrote: > This patch drops clean cache pages instead of migration during > alloc_contig_range() to minimise allocation latency by reducing the amount > of migration is necessary. It's useful for CMA because latency of migration > is more important than evicting the background processes working set. > In addition, as pages are reclaimed then fewer free pages for migration > targets are required so it avoids memory reclaiming to get free pages, > which is a contributory factor to increased latency. > > * from v1 > * drop migrate_mode_t > * add reclaim_clean_pages_from_list instad of MIGRATE_DISCARD support - Mel > > I measured elapsed time of __alloc_contig_migrate_range which migrates > 10M in 40M movable zone in QEMU machine. > > Before - 146ms, After - 7ms > > ... > > @@ -758,7 +760,9 @@ static unsigned long shrink_page_list(struct list_head *page_list, > wait_on_page_writeback(page); > } > > - references = page_check_references(page, sc); > + if (!force_reclaim) > + references = page_check_references(page, sc); grumble. Could we please document `enum page_references' and page_check_references()? And the `force_reclaim' arg could do with some documentation. It only forces reclaim under certain circumstances. They should be described, and a reson should be provided. Why didn't this patch use PAGEREF_RECLAIM_CLEAN? It is possible for someone to dirty one of these pages after we tested its cleanness and we'll then go off and write it out, but we won't be reclaiming it? > > ... > -- 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>