Messages in this thread | | | Date | Thu, 19 Jan 2006 19:10:07 +0100 | From | Nick Piggin <> | Subject | Re: [patch 2/4] mm: PageLRU no testset |
| |
On Thu, Jan 19, 2006 at 08:48:52PM +0300, Nikita Danilov wrote: > Nick Piggin writes: > > PG_lru is protected by zone->lru_lock. It does not need TestSet/TestClear > > operations. > > > > Signed-off-by: Nick Piggin <npiggin@suse.de> > > > > Index: linux-2.6/mm/vmscan.c > > =================================================================== > > --- linux-2.6.orig/mm/vmscan.c > > +++ linux-2.6/mm/vmscan.c > > @@ -775,9 +775,10 @@ int isolate_lru_page(struct page *page) > > if (PageLRU(page)) { > > struct zone *zone = page_zone(page); > > spin_lock_irq(&zone->lru_lock); > > - if (TestClearPageLRU(page)) { > > + if (PageLRU(page)) { > > ret = 1; > > get_page(page); > > + ClearPageLRU(page); > > Why is that better? ClearPageLRU() is also "atomic" operation (in the > sense of using LOCK_PREFIX on x86), so it seems this change strictly > adds cycles to the hot-path when page is on LRU. >
Less restrictive memory ordering requirements.
Nick
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |