lkml.org 
[lkml]   [2019]   [Mar]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [RFC][PATCH 6/8] perf/x86: Clear ->event_constraint[] on put
On Thu, Mar 14, 2019 at 6:11 AM Peter Zijlstra <peterz@infradead.org> wrote:
>
> The current code unconditionally clears cpuc->event_constraint[i]
> before calling get_event_constraints(.idx=i). The only site that cares
> is intel_get_event_constraints() where the c1 load will always be
> NULL.
>
> However, always calling get_event_constraints() on all events is
> wastefull, most times it will return the exact same result. Therefore
> retain the logic in intel_get_event_constraints() and change the
> generic code to only clear the constraint on put.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

I thought there was caching of the constraint in case it was static
(or unconstrained)
to avoid walking the constraint table each time between invocations
on the same group_sched_in() call. But the way the c1 vs. c2 logic
is written I don't see it. In which case, this could be another opportunity.

Looks good to me.

Reviewed-by: Stephane Eranian <eranian@google.com>

> ---
> arch/x86/events/core.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> --- a/arch/x86/events/core.c
> +++ b/arch/x86/events/core.c
> @@ -858,7 +858,6 @@ int x86_schedule_events(struct cpu_hw_ev
> x86_pmu.start_scheduling(cpuc);
>
> for (i = 0, wmin = X86_PMC_IDX_MAX, wmax = 0; i < n; i++) {
> - cpuc->event_constraint[i] = NULL;
> c = x86_pmu.get_event_constraints(cpuc, i, cpuc->event_list[i]);
> cpuc->event_constraint[i] = c;
>
> @@ -941,6 +940,8 @@ int x86_schedule_events(struct cpu_hw_ev
> */
> if (x86_pmu.put_event_constraints)
> x86_pmu.put_event_constraints(cpuc, e);
> +
> + cpuc->event_constraint[i] = NULL;
> }
> }
>
> @@ -1404,6 +1405,7 @@ static void x86_pmu_del(struct perf_even
> cpuc->event_list[i-1] = cpuc->event_list[i];
> cpuc->event_constraint[i-1] = cpuc->event_constraint[i];
> }
> + cpuc->event_constraint[i-1] = NULL;
> --cpuc->n_events;
>
> perf_event_update_userpage(event);
>
>

\
 
 \ /
  Last update: 2019-03-19 22:51    [W:0.191 / U:7.356 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site