linux-kernel - [PATCH 3/4] perf: Round robin flexible groups of events using list_rotate

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Message-Id: <1263649209-4343-4-git-send-regression-fweisbec@gmail.com>
Date:	Sat, 16 Jan 2010 14:40:08 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: [PATCH 3/4] perf: Round robin flexible groups of events using list_rotate_left()

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@...il.com>
Acked-by: Peter Zijlstra <peterz@...radead.org>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Arnaldo Carvalho de Melo <acme@...radead.org>
---
 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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