On Sun, 2017-02-12 at 14:05 +0900, Tejun Heo wrote: > > I think cgroup tree depth is a more significant issue; because of > > hierarchy we often do tree walks (uo-to-root or down-to-task). > > > > So creating elaborate trees is something I try not to do. > > So, as long as the depth stays reasonable (single digit or lower), > what we try to do is keeping tree traversal operations aggregated or > located on slow paths. There still are places that this overhead > shows up (e.g. the block controllers aren't too optimized) but it > isn't particularly difficult to make a handful of layers not matter at > all. A handful of cpu bean counting layers stings considerably. homer:/abuild # pipe-test 1 2.010057 usecs/loop -- avg 2.010057 995.0 KHz 2.006630 usecs/loop -- avg 2.009714 995.2 KHz 2.127118 usecs/loop -- avg 2.021455 989.4 KHz 2.256244 usecs/loop -- avg 2.044934 978.0 KHz 1.993693 usecs/loop -- avg 2.039810 980.5 KHz ^C homer:/abuild # cgexec -g cpu:hurt pipe-test 1 2.771641 usecs/loop -- avg 2.771641 721.6 KHz 2.432333 usecs/loop -- avg 2.737710 730.5 KHz 2.750493 usecs/loop -- avg 2.738988 730.2 KHz 2.663203 usecs/loop -- avg 2.731410 732.2 KHz 2.762564 usecs/loop -- avg 2.734525 731.4 KHz ^C homer:/abuild # cgexec -g cpu:hurt/pain pipe-test 1 2.967201 usecs/loop -- avg 2.967201 674.0 KHz 3.049012 usecs/loop -- avg 2.975382 672.2 KHz 3.031226 usecs/loop -- avg 2.980966 670.9 KHz 2.954259 usecs/loop -- avg 2.978296 671.5 KHz 2.933432 usecs/loop -- avg 2.973809 672.5 KHz ^C ... homer:/abuild # cgexec -g cpu:hurt/pain/ouch/moan/groan pipe-test 1 4.417044 usecs/loop -- avg 4.417044 452.8 KHz 4.494913 usecs/loop -- avg 4.424831 452.0 KHz 4.253861 usecs/loop -- avg 4.407734 453.7 KHz 4.378059 usecs/loop -- avg 4.404766 454.1 KHz 4.179895 usecs/loop -- avg 4.382279 456.4 KHz -- 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
