Hey everbody, I run following tests, and it shows in what cases this patch is beneficial for us. Test Environment: * Ubuntu Server 12.04.2 LTS Linux 3.2.0-40-virtual #64-Ubuntu on EC2. * 15 GB memory (DMA32 4GB + Normal 11GB). Test Settings: We have two PostgreSQL tables with same size of 9.75GB (65% of total memory), where these tables contain clickstream events for March and April. We call these two tables "events_march" and "events_april" respectively. Problem (Before Patch is Applied): I pass over events_march data twice with an example query, such as "select count(*) from events_march". This activates all of events_march's pages. I then pass over events_april dozens of times with a similar query. No matter how many times I query events_april, I can't get completely get this table's pages into memory. This happens even when events_march isn't touched at all, events_april easily fits into memory, and events_april has been referenced dozens of times. After Patch is Applied: This time, after three passes over events_april, all the pages are cached in memory. (4th access is completely served from memory.) I also repeated this test with a bigger dataset of size 12GB (80% of total memory) for both events_march and events_april, and observed the same results. (after 3rd pass, all of pages in events_april are cached.) Thank you, Metin On Wed, Aug 21, 2013 at 12:04 AM, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > On Sat, 17 Aug 2013 15:31:14 -0400 Johannes Weiner <hannes@xxxxxxxxxxx> wrote: > >> This series solves the problem by maintaining a history of pages >> evicted from the inactive list, enabling the VM to tell streaming IO >> from thrashing and rebalance the page cache lists when appropriate. > > I can't say I'm loving the patchset. It adds significant bloat to the > inode (of all things!), seems to add some runtime overhead and > certainly adds boatloads of complexity. > > In return for which we get... well, I don't know what we get - no data > was included. It had better be good! > > To aid in this decision, please go through the patchset and calculate > and itemize the overhead: increased inode size, increased radix-tree > consumption, lengthier code paths, anything else I missed Others can > make their own judgements regarding complexity increase. > > Then please carefully describe the benefits, then see if you can > convince us that one is worth the other! > -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
