On Thu 23-06-11 23:10:11, Hiroyuki Kamezawa wrote: > 2011/6/23 Michal Hocko <mhocko@xxxxxxx>: > > On Thu 16-06-11 12:57:41, KAMEZAWA Hiroyuki wrote: > >> From 4fbd49697456c227c86f1d5b46f2cd2169bf1c5b Mon Sep 17 00:00:00 2001 > >> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > >> Date: Thu, 16 Jun 2011 11:25:23 +0900 > >> Subject: [PATCH 7/7] memcg: proportional fair node vicitm selection > >> > >> commit 889976 implements a round-robin scan of numa nodes for > >> LRU scanning of memcg at hitting limit. > >> But, round-robin is not very good. > >> > >> This patch implements a proportionally fair victim selection of nodes > >> rather than round-robin. The logic is fair against each node's weight. > >> > >> Each node's weight is calculated periodically and we build an node's > >> scheduling entity as > >> > >> total_ticket = 0; > >> for_each_node(node) > >> node->ticket_start = total_ticket; > >> node->ticket_end = total_ticket + this_node's_weight() > >> total_ticket = node->ticket_end; > >> > >> Then, each nodes has some amounts of tickets in proportion to its own weight. > >> > >> At selecting victim, a random number is selected and the node which contains > >> the random number in [ticket_start, ticket_end) is selected as vicitm. > >> This is a lottery scheduling algorithm. > >> > >> For quick search of victim, this patch uses bsearch(). > >> > >> Test result: > >> on 8cpu box with 2 nodes. > >> limit memory to be 300MB and run httpd for 4096files/600MB working set. > >> do (normalized) random access by apache-bench and see scan_stat. > >> The test makes 40960 request. and see scan_stat. > >> (Because a httpd thread just use 10% cpu, the number of threads will > >> not be balanced between nodes. Then, file caches will not be balanced > >> between nodes.) > > > > Have you also tried to test with balanced nodes? I mean, is there any > > measurable overhead? > > > > Not enough yet. I checked OOM trouble this week :). > > I may need to make another fake_numa setup + cpuset > to measurements. What if you just use NUMA rotor for page cache? > In usual path, new overhead is random32() and > bsearch(). I'll do some. > > Thanks, > -Kame -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic -- 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>