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>
Reviewed-by: Stephane Eranian <eranian@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 9cab5ad..2795301 100644 (file)
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -858,7 +858,6 @@ int x86_schedule_events(struct cpu_hw_events *cpuc, int n, int *assign)
                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;
 
@@ -948,6 +947,8 @@ int x86_schedule_events(struct cpu_hw_events *cpuc, int n, int *assign)
                         */
                        if (x86_pmu.put_event_constraints)
                                x86_pmu.put_event_constraints(cpuc, e);
+
+                       cpuc->event_constraint[i] = NULL;
                }
        }
 
@@ -1411,6 +1412,7 @@ static void x86_pmu_del(struct perf_event *event, int flags)
                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);