perf/core: Add per perf_cpu_context min_heap storage

The storage required for visit_groups_merge's min heap needs to vary in
order to support more iterators, such as when multiple nested cgroups'
events are being visited. This change allows for 2 iterators and doesn't
support growth.

Based-on-work-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ian Rogers <irogers@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200214075133.181299-5-irogers@google.com

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 68e21e8..8768a39 100644 (file)
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -862,6 +862,13 @@ struct perf_cpu_context {
        int                             sched_cb_usage;
 
        int                             online;
+       /*
+        * Per-CPU storage for iterators used in visit_groups_merge. The default
+        * storage is of size 2 to hold the CPU and any CPU event iterators.
+        */
+       int                             heap_size;
+       struct perf_event               **heap;
+       struct perf_event               *heap_default[2];
 };
 
 struct perf_output_handle {

diff --git a/kernel/events/core.c b/kernel/events/core.c
index ddfb06c..7529e76 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3423,22 +3423,34 @@ static void __heap_add(struct min_heap *heap, struct perf_event *event)
        }
 }
 
-static noinline int visit_groups_merge(struct perf_event_groups *groups,
-                               int cpu,
+static noinline int visit_groups_merge(struct perf_cpu_context *cpuctx,
+                               struct perf_event_groups *groups, int cpu,
                                int (*func)(struct perf_event *, void *),
                                void *data)
 {
        /* Space for per CPU and/or any CPU event iterators. */
        struct perf_event *itrs[2];
-       struct min_heap event_heap = {
-               .data = itrs,
-               .nr = 0,
-               .size = ARRAY_SIZE(itrs),
-       };
-       struct perf_event **evt = event_heap.data;
+       struct min_heap event_heap;
+       struct perf_event **evt;
        int ret;
 
-       __heap_add(&event_heap, perf_event_groups_first(groups, -1));
+       if (cpuctx) {
+               event_heap = (struct min_heap){
+                       .data = cpuctx->heap,
+                       .nr = 0,
+                       .size = cpuctx->heap_size,
+               };
+       } else {
+               event_heap = (struct min_heap){
+                       .data = itrs,
+                       .nr = 0,
+                       .size = ARRAY_SIZE(itrs),
+               };
+               /* Events not within a CPU context may be on any CPU. */
+               __heap_add(&event_heap, perf_event_groups_first(groups, -1));
+       }
+       evt = event_heap.data;
+
        __heap_add(&event_heap, perf_event_groups_first(groups, cpu));
 
        min_heapify_all(&event_heap, &perf_min_heap);
@@ -3492,7 +3504,10 @@ ctx_pinned_sched_in(struct perf_event_context *ctx,
 {
        int can_add_hw = 1;
 
-       visit_groups_merge(&ctx->pinned_groups,
+       if (ctx != &cpuctx->ctx)
+               cpuctx = NULL;
+
+       visit_groups_merge(cpuctx, &ctx->pinned_groups,
                           smp_processor_id(),
                           merge_sched_in, &can_add_hw);
 }
@@ -3503,7 +3518,10 @@ ctx_flexible_sched_in(struct perf_event_context *ctx,
 {
        int can_add_hw = 1;
 
-       visit_groups_merge(&ctx->flexible_groups,
+       if (ctx != &cpuctx->ctx)
+               cpuctx = NULL;
+
+       visit_groups_merge(cpuctx, &ctx->flexible_groups,
                           smp_processor_id(),
                           merge_sched_in, &can_add_hw);
 }
@@ -10364,6 +10382,9 @@ skip_type:
                cpuctx->online = cpumask_test_cpu(cpu, perf_online_mask);
 
                __perf_mux_hrtimer_init(cpuctx, cpu);
+
+               cpuctx->heap_size = ARRAY_SIZE(cpuctx->heap_default);
+               cpuctx->heap = cpuctx->heap_default;
        }
 
 got_cpu_context: