On Tue, Mar 09, 2010 at 08:53:42PM +1100, Nick Piggin wrote: > Cool, you found this doesn't hurt performance too much? > Nothing outside the noise was measured. I didn't profile it to be absolutly sure but I expect it's ok. > Can't you remove the check from the reclaim code now? (The check > here should give a more timely wait anyway) > I'll try and see what the timing and total IO figures look like. > This is good because it should eliminate most all cases of extra > waiting. I wonder if you've also thought of doing the check in the > allocation path too as we were discussing? (this would give a better > FIFO behaviour under memory pressure but I could easily agree it is not > worth the cost) > I *could* make the check but as I noted in the leader, there isn't really a good test case that determines if these changes are "good" or "bad". Removing congestion_wait() seems like an obvious win but other modifications that alter how and when processes wait are less obvious. > On Mon, Mar 08, 2010 at 11:48:22AM +0000, Mel Gorman wrote: > > When a batch of pages have been freed to the buddy allocator, it is possible > > that it is enough to push a zone above its watermarks. This patch puts a > > check in the free path for zone pressure. It's in a common path but for > > the most part, it should only be checking if a linked list is empty and > > have minimal performance impact. > > > > Signed-off-by: Mel Gorman <mel@xxxxxxxxx> > > --- > > mm/page_alloc.c | 3 +++ > > 1 files changed, 3 insertions(+), 0 deletions(-) > > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index 1383ff9..3c8e8b7 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -562,6 +562,9 @@ static void free_pcppages_bulk(struct zone *zone, int count, > > } while (--count && --batch_free && !list_empty(list)); > > } > > spin_unlock(&zone->lock); > > + > > + /* A batch of pages have been freed so check zone pressure */ > > + check_zone_pressure(zone); > > } > > > > static void free_one_page(struct zone *zone, struct page *page, int order, > > -- > > 1.6.5 > -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>