On Mon, Sep 13, 2010 at 09:48:45PM +0800, Wu Fengguang wrote: > > + /* > > + * If reclaim is encountering dirty pages, it may be because > > + * dirty pages are reaching the end of the LRU even though the > > + * dirty_ratio may be satisified. In this case, wake flusher > > + * threads to pro-actively clean up to a maximum of > > + * 4 * SWAP_CLUSTER_MAX amount of data (usually 1/2MB) unless > > + * !may_writepage indicates that this is a direct reclaimer in > > + * laptop mode avoiding disk spin-ups > > + */ > > + if (file && nr_dirty_seen && sc->may_writepage) > > + wakeup_flusher_threads(nr_writeback_pages(nr_dirty)); > > wakeup_flusher_threads() works, but seems not the pertinent one. > > - locally, it needs some luck to clean the pages that direct reclaim is waiting on There is a certain amount of luck involved but it's depending on there being a correlation between old inodes and old pages on the LRU list. As long as that correlation is accurate, some relevant pages will get cleaned. Testing on previously released versions of this patch did show that the percentage of dirty pages encountered during reclaim were reduced as a result of this patch. > - globally, it cleans up some dirty pages, however some heavy dirtier > may quickly create new ones.. > > So how about taking the approaches in these patches? > > - "[PATCH 4/4] vmscan: transfer async file writeback to the flusher" > - "[PATCH 15/17] mm: lower soft dirty limits on memory pressure" > There is a lot going on in those patches. It's going to take me a while to figure them out and formulate an opinion. > In particular the first patch should work very nicely with memcg, as > all pages of an inode typically belong to the same memcg. So doing > write-around helps clean lots of dirty pages in the target LRU list in > one shot. > It might but as there is also a correlation between old dirty inodes and the location of dirty pages, it is tricky to predict if it is better and if so, by how much. -- 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>