[PATCH 3/4] perf: Round robin flexible groups of events using list_rotate_left()

[Frederic Weisbecker]

This is more proper that doing it through a list_for_each_entry()
that breaks after the first entry.

v2: Don't rotate pinned groups as its not needed to time share
them.

Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Acked-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxxxxx>
---
 kernel/perf_event.c |   17 ++++-------------
 1 files changed, 4 insertions(+), 13 deletions(-)

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index c9f8a75..bbebe28 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -1454,25 +1454,16 @@ static void perf_ctx_adjust_freq(struct perf_event_context *ctx)
  */
 static void rotate_ctx(struct perf_event_context *ctx)
 {
-	struct perf_event *event;
-
 	if (!ctx->nr_events)
 		return;
 
 	raw_spin_lock(&ctx->lock);
-	/*
-	 * Rotate the first entry last (works just fine for group events too):
-	 */
+
+	/* Rotate the first entry last of non-pinned groups */
 	perf_disable();
-	list_for_each_entry(event, &ctx->pinned_groups, group_entry) {
-		list_move_tail(&event->group_entry, &ctx->pinned_groups);
-		break;
-	}
 
-	list_for_each_entry(event, &ctx->flexible_groups, group_entry) {
-		list_move_tail(&event->group_entry, &ctx->flexible_groups);
-		break;
-	}
+	list_rotate_left(&ctx->flexible_groups);
+
 	perf_enable();
 
 	raw_spin_unlock(&ctx->lock);
-- 
1.6.2.3

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