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Subject[tip: perf/core] perf/core: Add per perf_cpu_context min_heap storage
The following commit has been merged into the perf/core branch of tip:

Commit-ID: 836196beb377e59e54ec9e04f7402076ef7a8bd8
Gitweb: https://git.kernel.org/tip/836196beb377e59e54ec9e04f7402076ef7a8bd8
Author: Ian Rogers <irogers@google.com>
AuthorDate: Thu, 13 Feb 2020 23:51:31 -08:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Fri, 06 Mar 2020 11:57:00 +01:00

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
---
include/linux/perf_event.h | 7 ++++++-
kernel/events/core.c | 43 +++++++++++++++++++++++++++----------
2 files changed, 39 insertions(+), 11 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 68e21e8..8768a39 100644
--- 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
--- 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:
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