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Subject[RFC][PATCH 6/8] perf/x86: Clear ->event_constraint[] on put
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>
---
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);

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