lkml.org 
[lkml]   [2019]   [Jul]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH v12 3/6] sched/core: uclamp: Propagate system defaults to root group
    On Thu, Jul 18, 2019 at 07:17:45PM +0100, Patrick Bellasi <patrick.bellasi@arm.com> wrote:
    > The clamp values are not tunable at the level of the root task group.
    > That's for two main reasons:
    >
    > - the root group represents "system resources" which are always
    > entirely available from the cgroup standpoint.
    >
    > - when tuning/restricting "system resources" makes sense, tuning must
    > be done using a system wide API which should also be available when
    > control groups are not.
    >
    > When a system wide restriction is available, cgroups should be aware of
    > its value in order to know exactly how much "system resources" are
    > available for the subgroups.
    IIUC, the global default would apply in uclamp_eff_get(), so this
    propagation isn't strictly necessary in order to apply to tasks (that's
    how it works under !CONFIG_UCLAMP_TASK_GROUP).
    The reason is that effective value (which isn't exposed currently) in a
    group takes into account this global restriction, right?


    > @@ -1043,12 +1063,17 @@ int sysctl_sched_uclamp_handler(struct ctl_table *table, int write,
    > [...]
    > + if (update_root_tg)
    > + uclamp_update_root_tg();
    > +
    > /*
    > * Updating all the RUNNABLE task is expensive, keep it simple and do
    > * just a lazy update at each next enqueue time.
    Since uclamp_update_root_tg() traverses down to
    uclamp_update_active_tasks() is this comment half true now?

    [unhandled content-type:application/pgp-signature]
    \
     
     \ /
      Last update: 2019-07-25 13:42    [W:9.285 / U:0.132 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site