Hi, On Tue, 19 Apr 2011 14:14:14 +0200 Michal Hocko <mhocko@xxxxxxx> wrote: > Hi, > > On Tue 29-03-11 09:21:22, Michal Hocko wrote: > > On Tue 29-03-11 10:15:11, Daisuke Nishimura wrote: > > [...] > > > From: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx> > > > > > > Since 569b846d(memcg: coalesce uncharge during unmap/truncate), we do batched > > > (delayed) uncharge at truncation/unmap. And since cdec2e42(memcg: coalesce > > > charging via percpu storage), we have percpu cache for res_counter. > > > > > > These changes improved performance of memory cgroup very much, but made > > > res_counter->usage usually have a bigger value than the actual value of memory usage. > > > So, *.usage_in_bytes, which show res_counter->usage, are not desirable for precise > > > values of memory(and swap) usage anymore. > > > > > > Instead of removing these files completely(because we cannot know res_counter->usage > > > without them), this patch updates the meaning of those files. > > > > > > Signed-off-by: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx> > > > --- > > > Documentation/cgroups/memory.txt | 15 +++++++++++++-- > > > 1 files changed, 13 insertions(+), 2 deletions(-) > > > > > > diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt > > > index 7781857..4f49d91 100644 > > > --- a/Documentation/cgroups/memory.txt > > > +++ b/Documentation/cgroups/memory.txt > > > @@ -52,8 +52,10 @@ Brief summary of control files. > > > tasks # attach a task(thread) and show list of threads > > > cgroup.procs # show list of processes > > > cgroup.event_control # an interface for event_fd() > > > - memory.usage_in_bytes # show current memory(RSS+Cache) usage. > > > - memory.memsw.usage_in_bytes # show current memory+Swap usage > > > + memory.usage_in_bytes # show current res_counter usage for memory > > > + (See 5.5 for details) > > > + memory.memsw.usage_in_bytes # show current res_counter usage for memory+Swap > > > + (See 5.5 for details) > > > memory.limit_in_bytes # set/show limit of memory usage > > > memory.memsw.limit_in_bytes # set/show limit of memory+Swap usage > > > memory.failcnt # show the number of memory usage hits limits > > > @@ -453,6 +455,15 @@ memory under it will be reclaimed. > > > You can reset failcnt by writing 0 to failcnt file. > > > # echo 0 > .../memory.failcnt > > > > > > +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 memory(and swap) usage, it's an fuzz > > > +value for efficient access. (Of course, when necessary, it's synchronized.) > > > +If you want to know more exact memory usage, you should use RSS+CACHE(+SWAP) > > > +value in memory.stat(see 5.2). > > > + > > > 6. Hierarchy support > > > > > > The memory controller supports a deep hierarchy and hierarchical accounting. > > > > Acked-by: Michal Hocko <mhocko@xxxxxxx> > > > > Although I would like to see a mention about what is the reason for > > keeping that file(s) if their usage is very limited. Something like. > > "We are keeping the file because we want to be consistent with other > > cgroups implementations and all of them export usage counter in some > > way. Make sure you exactly know the meaning before you use the value > > in userspace." > > > > If nobody else feels that this is that important then please forget > > about this comment. > > I am wondering what happened to the patch. Do you have any plans to > update/push it? > Ouch! Thank you for your reminding me.. I'll resend this to Andrew soon. Thanks, Daisuke Nishimura. -- 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>