linux-kernel - [PATCH 5/6] perf: Don't rotate pinned groups

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Message-Id: <1263087500-14215-6-git-send-regression-fweisbec@gmail.com>
Date:	Sun, 10 Jan 2010 02:38:19 +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>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Paul Mackerras <paulus@...ba.org>
Subject: [PATCH 5/6] perf: Don't rotate pinned groups

We round-robin pinned groups, which means we make them behaving
just like non-pinned groups. Currently, and in practice, the almost
only difference between pinned and non-pinned events is that the
formers are scheduled before the latters. And the latters also
stop scheduling non-software-only groups once one couldn't make
it.

Anyway, pinned groups don't need to be round-robined because if
a pinned group can't be scheduled, it is going to be put in an
error state, following the pinned logic: it is always or never
scheduled in a context.

Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Paul Mackerras <paulus@...ba.org>
---
 kernel/perf_event.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 7d00676..584e854 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -1451,11 +1451,10 @@ static void rotate_ctx(struct perf_event_context *ctx)
 
 	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_rotate_left(&ctx->pinned_groups);
 	list_rotate_left(&ctx->flexible_groups);
 
 	perf_enable();
-- 
1.6.2.3

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