On Tue, Aug 29, 2017 at 08:24:27AM -0700, Tejun Heo wrote: > Hello, Peter. > > On Tue, Aug 29, 2017 at 04:32:52PM +0200, Peter Zijlstra wrote: > > So I mostly like. On accounting it only adds to the immediate cgroup (if > > it has a parent, aka !root). > > > > On update it does a DFS of all sub-groups and propagates the deltas up > > to the requested group. > ... > > What I don't get is why you need cgroup_cpu_stat_updated(). That is, I > > see you use it to keep the keep the DFS 'stack' up-to-date, but what I > > don't see is why you'd need that. > > That is to make reading stats O(number of descendants which have been > active since last read) instad of O(number of all descendants) as > there can be a lot of not-too-active cgroups in a system. Stat > reading can be frequent, so the combination can get really bad. By > keeping the updated list separate, increasing read frequency decreases > the cost of each read. Hmm, and when its never read, we only do the O(depth) thing _once_, right? -- 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
