lkml.org 
[lkml]   [2010]   [Mar]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [PATCH] perf_events: improve task_sched_in()
    From
    Date
    On Wed, 2010-03-10 at 22:26 -0800, eranian@google.com wrote:
    > This patch is an optimization in perf_event_task_sched_in() to avoid scheduling
    > the events twice in a row. Without it, the perf_disable()/perf_enable() pair
    > is invoked twice, thereby pinned events counts while scheduling flexible events
    > and we go throuh hw_perf_enable() twice. By encapsulating, the whole sequence
    > into perf_disable()/perf_enable() we ensure, hw_perf_enable() is going to be
    > invoked only once because of the refcount protection.

    Agreed, this makes perfect sense.

    Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>

    > Signed-off-by: Stephane Eranian <eranian@google.com>
    > --
    > perf_event.c | 4 ++++
    > 1 file changed, 4 insertions(+)
    >
    > --- a/kernel/perf_event.c
    > +++ b/kernel/perf_event.c
    > @@ -1382,6 +1382,8 @@ void perf_event_task_sched_in(struct task_struct *task)
    > if (cpuctx->task_ctx == ctx)
    > return;
    >
    > + perf_disable();
    > +
    > /*
    > * We want to keep the following priority order:
    > * cpu pinned (that don't need to move), task pinned,
    > @@ -1394,6 +1396,8 @@ void perf_event_task_sched_in(struct task_struct *task)
    > ctx_sched_in(ctx, cpuctx, EVENT_FLEXIBLE);
    >
    > cpuctx->task_ctx = ctx;
    > +
    > + perf_enable();
    > }
    >
    > #define MAX_INTERRUPTS (~0ULL)



    \
     
     \ /
      Last update: 2010-03-11 09:37    [W:0.033 / U:125.428 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site