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Subject[RFC][PATCH 7/8] perf/x86: Optimize x86_schedule_events()
Now that cpuc->event_constraint[] is retained, we can avoid calling
get_event_constraints() over and over again.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/events/core.c | 25 +++++++++++++++++++++----
arch/x86/events/intel/core.c | 3 ++-
2 files changed, 23 insertions(+), 5 deletions(-)

--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -844,6 +844,12 @@ int perf_assign_events(struct event_cons
}
EXPORT_SYMBOL_GPL(perf_assign_events);

+static inline bool is_ht_workaround_active(struct cpu_hw_events *cpuc)
+{
+ return is_ht_workaround_enabled() && !cpuc->is_fake &&
+ READ_ONCE(cpuc->excl_cntrs->exclusive_present);
+}
+
int x86_schedule_events(struct cpu_hw_events *cpuc, int n, int *assign)
{
struct event_constraint *c;
@@ -858,8 +864,20 @@ 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++) {
- c = x86_pmu.get_event_constraints(cpuc, i, cpuc->event_list[i]);
- cpuc->event_constraint[i] = c;
+ c = cpuc->event_constraint[i];
+
+ /*
+ * Request constraints for new events; or for those events that
+ * have a dynamic constraint due to the HT workaround -- for
+ * those the constraint can change due to scheduling activity
+ * on the other sibling.
+ */
+ if (!c || ((c->flags & PERF_X86_EVENT_DYNAMIC) &&
+ is_ht_workaround_active(cpuc))) {
+
+ c = x86_pmu.get_event_constraints(cpuc, i, cpuc->event_list[i]);
+ cpuc->event_constraint[i] = c;
+ }

wmin = min(wmin, c->weight);
wmax = max(wmax, c->weight);
@@ -903,8 +921,7 @@ int x86_schedule_events(struct cpu_hw_ev
* N/2 counters can be used. This helps with events with
* specific counter constraints.
*/
- if (is_ht_workaround_enabled() && !cpuc->is_fake &&
- READ_ONCE(cpuc->excl_cntrs->exclusive_present))
+ if (is_ht_workaround_active(cpuc))
gpmax /= 2;

unsched = perf_assign_events(cpuc->event_constraint, n, wmin,
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -2945,7 +2945,8 @@ intel_get_event_constraints(struct cpu_h
* - dynamic constraint: handled by intel_get_excl_constraints()
*/
c2 = __intel_get_event_constraints(cpuc, idx, event);
- if (c1 && (c1->flags & PERF_X86_EVENT_DYNAMIC)) {
+ if (c1) {
+ WARN_ON_ONCE(!(c1->flags & PERF_X86_EVENT_DYNAMIC));
bitmap_copy(c1->idxmsk, c2->idxmsk, X86_PMC_IDX_MAX);
c1->weight = c2->weight;
c2 = c1;

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