On Tue, Mar 09, 2010 at 10:08:35AM +0000, Mel Gorman wrote: > 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. OK. Moving the waitqueue cacheline out of the fastpath footprint and doing the flag thing might be a good idea? > > 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. Well reclaim goes through free_pages_bulk anyway, doesn't it? So I don't see why you would have to run any test. > > 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. Fair enough. But we could be sure it increases fairness, which is a good thing. So then we'd just have to check it against performance. Your patches seem like a good idea regardless of this issue, don't get me wrong. -- 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>