Commit-ID: 8703a7cfe148f73062c568e9a8549ce692104864
Gitweb: https://git.kernel.org/tip/8703a7cfe148f73062c568e9a8549ce692104864
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Mon, 13 Nov 2017 14:28:44 +0100
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Mon, 12 Mar 2018 15:28:50 +0100
perf/core: Fix tree based event rotation
Similar to how first programming cpu=-1 and then cpu=# is wrong, so is
rotating both. It was especially wrong when we were still programming
the PMU in this same order, because in that scenario we might never
actually end up running cpu=# events at all.
Cure this by using the active_list to pick the rotation event; since
at programming we already select the left-most event.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Acked-by: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Alexey Budankov <alexey.budankov@xxxxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: David Carrillo-Cisneros <davidcc@xxxxxxxxxx>
Cc: Dmitri Prokhorov <Dmitry.Prohorov@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Kan Liang <kan.liang@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Valery Cherepennikov <valery.cherepennikov@xxxxxxxxx>
Cc: Vince Weaver <vincent.weaver@xxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/events/core.c | 44 ++++++++++++++++++--------------------------
1 file changed, 18 insertions(+), 26 deletions(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index fc5dd072c194..460e485220e8 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1623,22 +1623,6 @@ perf_event_groups_next(struct perf_event *event)
return NULL;
}
-/*
- * Rotate the @cpu subtree.
- *
- * Re-insert the leftmost event at the tail of the subtree.
- */
-static void
-perf_event_groups_rotate(struct perf_event_groups *groups, int cpu)
-{
- struct perf_event *event = perf_event_groups_first(groups, cpu);
-
- if (event) {
- perf_event_groups_delete(groups, event);
- perf_event_groups_insert(groups, event);
- }
-}
-
/*
* Iterate through the whole groups tree.
*/
@@ -3601,24 +3585,24 @@ static void perf_adjust_freq_unthr_context(struct perf_event_context *ctx,
}
/*
- * Round-robin a context's events:
+ * Move @event to the tail of the @ctx's elegible events.
*/
-static void rotate_ctx(struct perf_event_context *ctx)
+static void rotate_ctx(struct perf_event_context *ctx, struct perf_event *event)
{
/*
* Rotate the first entry last of non-pinned groups. Rotation might be
* disabled by the inheritance code.
*/
- if (!ctx->rotate_disable) {
- int sw = -1, cpu = smp_processor_id();
+ if (ctx->rotate_disable)
+ return;
- perf_event_groups_rotate(&ctx->flexible_groups, sw);
- perf_event_groups_rotate(&ctx->flexible_groups, cpu);
- }
+ perf_event_groups_delete(&ctx->flexible_groups, event);
+ perf_event_groups_insert(&ctx->flexible_groups, event);
}
static int perf_rotate_context(struct perf_cpu_context *cpuctx)
{
+ struct perf_event *ctx_event = NULL, *cpuctx_event = NULL;
struct perf_event_context *ctx = NULL;
int rotate = 0;
@@ -3639,13 +3623,21 @@ static int perf_rotate_context(struct perf_cpu_context *cpuctx)
perf_ctx_lock(cpuctx, cpuctx->task_ctx);
perf_pmu_disable(cpuctx->ctx.pmu);
+ cpuctx_event = list_first_entry_or_null(&cpuctx->ctx.flexible_active,
+ struct perf_event, active_list);
+ if (ctx) {
+ ctx_event = list_first_entry_or_null(&ctx->flexible_active,
+ struct perf_event, active_list);
+ }
+
cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE);
if (ctx)
ctx_sched_out(ctx, cpuctx, EVENT_FLEXIBLE);
- rotate_ctx(&cpuctx->ctx);
- if (ctx)
- rotate_ctx(ctx);
+ if (cpuctx_event)
+ rotate_ctx(&cpuctx->ctx, cpuctx_event);
+ if (ctx_event)
+ rotate_ctx(ctx, ctx_event);
perf_event_sched_in(cpuctx, ctx, current);
--
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