[Resending because gmail doesn't understand when to go plaintext :-) ] [Added a few other folks who might have something to say about it] On Fri, Nov 25, 2016 at 9:34 AM, Marat Khalili <mkh@xxxxxx> wrote: > I have a question as a cgroup cpu limits user: how does it interact with > nice? Documentation creates the impression that, as long as number of > processes demanding the cpu time exceeds number of available cores, time > allocated will be proportional to configured cpu.shares. However, in > practice I observe that group with niced processes significantly under > perform. > > For example, suppose on a 6-core box /cgroup/cpu/group1/cpu.shares is 400, > and /cgroup/cpu/group2/cpu.shares is 200. > 1) If I run `stress -c 6` in both groups, I should see approximately 400% of > cpu time in group1 and 200% in group2 in top output, regardless of their > relative nice value. > 2) If I run `nice -n 19 stress -c 1` in cgroup1 and `stress -c 24` in > group2, I should see at least 100% of cpu time in group1. > > What I see is significantly less cpu time in group1 if group1 processes > happen to have greater nice value, and especially if group2 have greater > number of processes involved: cpu load of group1 in example 2 can be as low > as 20%. It may create tensions among users in my case; how can this be > avoided except by renicing all processes to the same value? > >> $ uname -a >> Linux redacted 2.6.32-642.11.1.el6.x86_64 #1 SMP Fri Nov 18 19:25:05 UTC >> 2016 x86_64 x86_64 x86_64 GNU/Linux > This is an old version of the kernel. Do you see the same behavior on a newer version of the kernel? (4.8 is the latest stable kernel) > >> $ lsb_release -a >> LSB Version: >> :base-4.0-amd64:base-4.0-noarch:core-4.0-amd64:core-4.0-noarch:graphics-4.0-amd64:graphics-4.0-noarch:printing-4.0-amd64:printing-4.0-noarch >> Distributor ID: CentOS >> Description: CentOS release 6.8 (Final) >> Release: 6.8 >> Codename: Final > > > (My apologies if I'm posting to incorrect list.) > > -- > > With Best Regards, > Marat Khalili > -- Thanks, Dhaval -- 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
