On Fri, Nov 18, 2011 at 05:43:08PM +0100, Marek Szyprowski wrote: > From: Michal Nazarewicz <mina86@xxxxxxxxxx> > > If page is on PCP list while pageblock it belongs to gets isolated, > the page's private still holds the old migrate type. This means > that free_pcppages_bulk() will put the page on a freelist of the > old migrate type instead of MIGRATE_ISOLATE. > > This commit changes that by explicitly checking whether page's > pageblock's migrate type is MIGRATE_ISOLATE and if it is, overwrites > page's private data. > > Signed-off-by: Michal Nazarewicz <mina86@xxxxxxxxxx> > Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> > --- > mm/page_alloc.c | 12 ++++++++++++ > 1 files changed, 12 insertions(+), 0 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 9dd443d..58d1a2e 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -628,6 +628,18 @@ static void free_pcppages_bulk(struct zone *zone, int count, > page = list_entry(list->prev, struct page, lru); > /* must delete as __free_one_page list manipulates */ > list_del(&page->lru); > + > + /* > + * When page is isolated in set_migratetype_isolate() > + * function it's page_private is not changed since the > + * function has no way of knowing if it can touch it. > + * This means that when a page is on PCP list, it's > + * page_private no longer matches the desired migrate > + * type. > + */ > + if (get_pageblock_migratetype(page) == MIGRATE_ISOLATE) > + set_page_private(page, MIGRATE_ISOLATE); > + How much of a problem is this in practice? It's adding overhead to the free path for what should be a very rare case which is undesirable. I know we are already calling get_pageblock_migrate() when freeing pages but it should be unnecessary to call it again. I'd go as far to say that it would be preferable to drain the per-CPU lists after you set pageblocks MIGRATE_ISOLATE. The IPIs also have overhead but it will be incurred for the rare rather than the common case. -- Mel Gorman SUSE Labs -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>