On Mon 28-03-11 18:11:27, KAMEZAWA Hiroyuki wrote: > On Mon, 28 Mar 2011 09:43:42 +0200 > Michal Hocko <mhocko@xxxxxxx> wrote: > > > On Mon 28-03-11 13:25:50, Daisuke Nishimura wrote: > > > From: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx> [...] > > > +5.5 usage_in_bytes > > > + > > > +As described in 2.1, memory cgroup uses res_counter for tracking and limiting > > > +the memory usage. memory.usage_in_bytes shows the current res_counter usage for > > > +memory, and DOESN'T show a actual usage of RSS and Cache. It is usually bigger > > > +than the actual usage for a performance improvement reason. > > > > Isn't an explicit mention about caching charges better? > > > > It's difficult to distinguish which is spec. and which is implemnation details... Sure. At least commit log should contain the implementation details IMO, though. > > My one here ;) > == > 5.5 usage_in_bytes > > For efficiency, as other kernel components, memory cgroup uses some optimization to > avoid unnecessary cacheline false sharing. usage_in_bytes is affected by the > method and doesn't show 'exact' value of usage, it's an fuzz value for efficient > access. (Of course, when necessary, it's synchronized.) > In usual, the value (RSS+CACHE) in memory.stat shows more exact value. IOW, - In usual, the value (RSS+CACHE) in memory.stat shows more exact value. IOW, + (RSS+CACHE) value from memory.stat shows more exact value and should be used + by userspace. IOW, ? > usage_in_bytes is less exact than memory.stat. The error will be larger on the larger > hardwares which have many cpus and tasks. > == > > Hmm ? Looks much better. Thanks -- 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@xxxxxxxxxx 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>