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items: Re: A strange behavior of sched_fair

Re: A strange behavior of sched_fair
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description: (cc containers list) On Wed, 27 Feb 2008 17:51:35 -0500 Kei Tokunaga <tokunaga.keiich@jp.fujitsu.com> wrote: > Hi Ingo, > > I am playing around with sched_fair and cgroup, and it seems like > I hit a possible bug. Could you also check if that is a bug? > > Description of behavior: > Start a cpu-bound task (t1), attach it to a cgroup (cgA), and let the > task to run for a while (e.g. several tens of seconds or a couple of > minutes would be adequate.) Then, start another cpu-bound task (t2) > and attach it to cgA in the way described in "Steps to Reproduce" section. > You will see t1 does not get run for a while. > (The tasks may not have to be cpu-bound, but it is easier to see the > behavior using cpu-bound tasks.) > > How reproducible: > Always. > > Environments where I saw the behavior: > 2.6.25-rc3 with resource management functions enabled on ia64 box. > > Steps to Reproduce: > # mkdir /dev/cgroup > # mount -t cgroup -ocpuset,cpu cpu /dev/cgroup > # mkdir /dev/cgroup/{a,b} > # echo 0 > /dev/cgroup/a/cpuset.cpus > # echo 0 > /dev/cgroup/b/cpuset.cpus > # echo 1 > /dev/cgroup/a/cpuset.mems > # echo 1 > /dev/cgroup/b/cpuset.mems > # echo $$ > /dev/cgroup/b/tasks > # ./a.out & echo $! > /dev/cgroup/a/tasks (a.out is just a for-loop program) > [Wait for several tens of seconds or a couple of minutes.] > # ./a.out2 & echo $! > /dev/cgroup/a/tasks (a.out2 is just a for-loop program) > [You will see a.out does not get run for a while by running top command.] > > Additional Info: > a.out2 needs to be started from the shell of cgroup-b in order to > reproduce the problem (, unless the system is UP.) Starting a.out2 > in the manner, se->vruntime (or something to create the se->vruntime) > of a.out2 seems to be initialized to a small value, compared to the > value of a.out. And the fair scheduler only runs a.out2 until the > se->vruntime catches up with the se->vruntime of a.out. > > Thanks, > Kei > -- > Kei Tokunaga > Fujitsu (Red Hat On-site Partner) ____________________…
creator: akpm
date: 2008-02-29T07:08:20-00:00