On Thu 17-05-12 02:24:12, Andrew Morton wrote: > On Thu, 17 May 2012 11:13:53 +0200 Michal Hocko <mhocko@xxxxxxx> wrote: > > > [64574746 vmscan: detect mapped file pages used only once] made mapped pages > > have another round in inactive list because they might be just short > > lived and so we could consider them again next time. This heuristic > > helps to reduce pressure on the active list with a streaming IO > > worklods. > > This patch fixes a regression introduced by this commit for heavy shmem > > A performance regression, specifically. > > Are you able to quantify it? The customer's workload is shmem backed database (80% of RAM) and they are measuring transactions/s with an IO in the background (20%). Transactions touch more or less random rows in the table. The rate goes down drastically when we start swapping out memory. Numbers are more descriptive (without the patch is 100%, with 5 representative runs) Average rate 315.83% Best rate 131.76% Worst rate 641.25% Standard deviation (calibrated to average) is ~4% while without the patch we are at 62.82%. The big variance without the patch is caused by the excessive swapping which doesn't occur with the patch applied. * Worst run (100%) compared to a random run with the patch pgpgin pswpin pswpout pgmajfault 1.58% 0.00% 0.01% 0.22% Average size of the LRU lists: nr_inactive_anon nr_active_anon nr_inactive_file nr_active_file 52.91% 7234.72% 249.39% 126.64% * Best run pgpgin pswpin pswpout pgmajfault 3.37% 0.00% 0.11% 0.39% nr_inactive_anon nr_active_anon nr_inactive_file nr_active_file 49.85% 3868.74% 175.03% 121.27% -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 -- 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>