[lkml]   [2011]   [Dec]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [RFC PATCH 0/4] Gang scheduling in CFS
    On Mon, 2011-12-19 at 16:51 +0100, Peter Zijlstra wrote:
    > On Mon, 2011-12-19 at 14:03 +0530, Nikunj A. Dadhania wrote:
    > > The following patches implements gang scheduling. These patches
    > > are *highly* experimental in nature and are not proposed for
    > > inclusion at this time.
    > Nor will they ever be, I've always strongly opposed the whole concept
    > and I'm not about to change my mind. Gang scheduling is a scalability
    > nightmare.
    > > Gang scheduling can be helpful in virtualization scenario. It will
    > > help in avoiding the lock-holder-preemption[1] problem and other
    > > benefits include improved lock-acquisition times. This feature
    > > will help address some limitations of KVM on Power
    > Use paravirt ticket locks or a pause-loop-filter like thing.
    > > On Power, we have an interesting hardware restriction on guests
    > > running across SMT theads: on any single core, we can only run one
    > > mm context at any given time.
    > OMFG are your hardware engineers insane?

    No we can run separate mm contexts, but we can only run one -partition-
    at a time. Sadly the host kernel is also a partition for the MMU so that
    means that all 4 threads must be running the same guest and enter/exit
    the guest at the same time.

    > Anyway, I had a look at your patches and I don't see how could ever
    > work. You gang-schedule cgroup entities, but there's no guarantee the
    > load-balancer will have at least one task for each group on every cpu.


     \ /
      Last update: 2011-12-19 23:13    [W:0.033 / U:4.288 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site