On Thu, Apr 15, 2010 at 05:26:27PM +0900, KOSAKI Motohiro wrote: > Cc to Johannes > > > > > > > On Apr 14, 2010, at 9:11 PM, KOSAKI Motohiro wrote: > > > > > > > Now, vmscan pageout() is one of IO throuput degression source. > > > > Some IO workload makes very much order-0 allocation and reclaim > > > > and pageout's 4K IOs are making annoying lots seeks. > > > > > > > > At least, kswapd can avoid such pageout() because kswapd don't > > > > need to consider OOM-Killer situation. that's no risk. > > > > > > > > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> > > > > > > What's your opinion on trying to cluster the writes done by pageout, > > > instead of not doing any paging out in kswapd? > > > Something along these lines: > > > > Interesting. > > So, I'd like to review your patch carefully. can you please give me one > > day? :) > > Hannes, if my remember is correct, you tried similar swap-cluster IO > long time ago. now I can't remember why we didn't merged such patch. > Do you remember anything? Oh, quite vividly in fact :) For a lot of swap loads the LRU order diverged heavily from swap slot order and readaround was a waste of time. Of course, the patch looked good, too, but it did not match reality that well. I guess 'how about this patch?' won't get us as far as 'how about those numbers/graphs of several real-life workloads? oh and here is the patch...'. > > > Cluster writes to disk due to memory pressure. > > > > > > Write out logically adjacent pages to the one we're paging out > > > so that we may get better IOs in these situations: > > > These pages are likely to be contiguous on disk to the one we're > > > writing out, so they should get merged into a single disk IO. > > > > > > Signed-off-by: Suleiman Souhlal <suleiman@xxxxxxxxxx> For random IO, LRU order will have nothing to do with mapping/disk order. -- 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>