On Wed, Nov 17, 2010 at 03:46:41PM -0800, Andrew Morton wrote: > On Wed, 17 Nov 2010 16:22:41 +0000 > Mel Gorman <mel@xxxxxxxxx> wrote: > > > Huge page allocations are not expected to be cheap but lumpy reclaim > > is still very disruptive. > > Huge pages are boring. Can we expect any benefit for the > stupid-nic-driver-which-does-order-4-GFP_ATOMIC-allocations problem? > Yes. Specifically, while GFP_ATOMIC allocations still cannot enter compaction (although with asynchronous migration, it's closer), kswapd will react faster. As a result, it should be harder to trigger allocation failures. Huge pages are simply the worst case in terms of allocation latency which is why I tend to focus testing on them. That, and I don't have a suitable pair of machines with one of these order-4-atomic-stupid-nics. > > I haven't pushed hard on the concept of lumpy compaction yet and right > > now I don't intend to during this cycle. The initial prototypes did not > > behave as well as expected and this series improves the current situation > > a lot without introducing new algorithms. Hence, I'd like this series to > > be considered for merging. > > Translation: "Andrew, wait for the next version"? :) > Preferably do not wait unless review reveals a major flaw. Lumpy compaction in its initial prototype versions simply did not work out as a good policy modification and requires much deeper thought. This series was effective at getting latencies down to the level I expected lumpy compaction to. If I do make lumpy compaction work properly, its effect will be to reduce scanning rates but the latencies are likely to be similar. > > I'm hoping that this series also removes the > > necessity for the "delete lumpy reclaim" patch from the THP tree. > > Now I'm sad. I read all that and was thinking "oh goody, we get to > delete something for once". But no :( > > If you can get this stuff to work nicely, why can't we remove lumpy > reclaim? Ultimately we should be able to. Lumpy reclaim is still there for the !CONFIG_COMPACTION case and to have an option if we find that compaction behaves badly for some reason. -- 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/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>