On Tue 21-07-15 13:32:23, Nikolay Borisov wrote: > > > On 07/21/2015 12:48 PM, Michal Hocko wrote: > > On Tue 21-07-15 12:08:40, Nikolay Borisov wrote: [...] > >> I looked more carefully into the code and saw that the page_counters > >> (which back memory/memsw.limit/usage_in_bytes) are charged during the > >> try_charge whereas the per-cpu statistics (which back the info in > >> memory.stats) are updated after committing the charge. I assume in the > >> case where charges are not canceled the data in memory.stats and > >> memory.memsw.max_usage_in_bytes - memory.usage_in_bytes should be identical? > > > > I am not sure what you mean here. max_usage_in_bytes is a historical > > value which was the maximum charge used at some point in time. > > usage_in_bytes is always the _current_ value of the charge counter. > > max_usage_in_bytes-usage_in_bytes doesn't tell you much really. > > > > I have misunderstood me I have never, ever referred to max_usage. What I > meant was that the information that memory.stat file provides is > acquired by reading the memcg->stat->count[counter] and those values are > updated when mem_cgroup_commit_charge() is invoked. True > And > mem_cgroup_commit_charge is invoked AFTER mem_cgroup_try_charge, which > updates the charge counters. Still true and you should realize that the commit is called very shortly after the charge. The race window is not really interesting for anything practical. > So my point was that whether I read the > swap value (for example) from the memory.stats file or whether I > manually do the maths with subtraction as previously shown the 2 values > should match. Your subtraction simply doesn't work and doesn't tell you how much memory is swapped out from the memcg as explained in other email. > Essentially whether information should be queried form the charge > counter or from the mem_cgroup_stat_cpu struct. Does that make sense? memory.stat will tell you the information you are looking for. You simply cannot calculate those numbers from the counters. -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
