On Mon, Aug 08, 2011 at 04:18:11PM +0400, Konstantin Khlebnikov wrote: > Pekka Enberg wrote: > >Hi Konstantin, > > > >On Mon, Aug 8, 2011 at 2:06 PM, Konstantin Khlebnikov > ><khlebnikov@xxxxxxxxxx> wrote: > >>Commit v2.6.33-5448-g6457474 (vmscan: detect mapped file pages used only once) > >>greatly decreases lifetime of single-used mapped file pages. > >>Unfortunately it also decreases life time of all shared mapped file pages. > >>Because after commit v2.6.28-6130-gbf3f3bc (mm: don't mark_page_accessed in fault path) > >>page-fault handler does not mark page active or even referenced. > >> > >>Thus page_check_references() activates file page only if it was used twice while > >>it stays in inactive list, meanwhile it activates anon pages after first access. > >>Inactive list can be small enough, this way reclaimer can accidentally > >>throw away any widely used page if it wasn't used twice in short period. > >> > >>After this patch page_check_references() also activate file mapped page at first > >>inactive list scan if this page is already used multiple times via several ptes. > >> > >>Signed-off-by: Konstantin Khlebnikov<khlebnikov@xxxxxxxxxx> > > > >Both patches seem reasonable but the changelogs don't really explain > >why you're doing the changes. How did you find out about the problem? > >Is there some workload that's affected? How did you test your changes? > > > > I found this while trying to fix degragation in rhel6 (~2.6.32) from rhel5 (~2.6.18). > There a complete mess with >100 web/mail/spam/ftp containers, > they share all their files but there a lot of anonymous pages: > ~500mb shared file mapped memory and 15-20Gb non-shared anonymous memory. How much unmapped cache do you have around in this scenario? > In this situation major-pagefaults are very costly, because all containers share the same page. > In my load kernel created a disproportionate pressure on the file memory, compared with the anonymous, > they equaled only if I raise swappiness up to 150 =) > > These patches actually wasn't helped a lot in my problem, > but I saw noticable (10-20 times) reduce in count and average time of major-pagefault in file-mapped areas. If disabling the used-once detection for shared executable pages does not help, then the real reason for the regression you observe seems to be a different one. Reduced major faults in file mapped areas without other context don't have to be a good sign per se. Which memory was reclaimed instead? Did swapping increase? It would be good to find a fix that actually helps your workload. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>