linux-kernel - [PATCH 2/2] oprofile: Remove 'WQ on CPUx, prefer CPUy' warning

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Date:	Fri, 24 Aug 2012 20:53:31 +0200
From:	Robert Richter <robert.richter@....com>
To:	Ingo Molnar <mingo@...nel.org>
CC:	LKML <linux-kernel@...r.kernel.org>,
	oprofile-list <oprofile-list@...ts.sourceforge.net>,
	Robert Richter <robert.richter@....com>,
	Andi Kleen <andi@...stfloor.org>
Subject: [PATCH 2/2] oprofile: Remove 'WQ on CPUx, prefer CPUy' warning

Under certain workloads we see the following warnings:

 WQ on CPU0, prefer CPU1
 WQ on CPU0, prefer CPU2
 WQ on CPU0, prefer CPU3

It warns the user that the wq to access a per-cpu buffers runs not on
the same cpu. This happens if the wq is rescheduled on a different cpu
than where the buffer is located. This was probably implemented to
detect performance issues. Not sure if there actually is one as the
buffers are copied to a single buffer anyway which should be the
actual bottleneck.

We wont change WQ implementation. Since a user can do nothing the
warning is pointless. Removing it.

Cc: Andi Kleen <andi@...stfloor.org>
Signed-off-by: Robert Richter <robert.richter@....com>
---
 drivers/oprofile/cpu_buffer.c |   11 +++--------
 1 files changed, 3 insertions(+), 8 deletions(-)

diff --git a/drivers/oprofile/cpu_buffer.c b/drivers/oprofile/cpu_buffer.c
index b8ef8dd..8aa73fa 100644
--- a/drivers/oprofile/cpu_buffer.c
+++ b/drivers/oprofile/cpu_buffer.c
@@ -451,14 +451,9 @@ static void wq_sync_buffer(struct work_struct *work)
 {
 	struct oprofile_cpu_buffer *b =
 		container_of(work, struct oprofile_cpu_buffer, work.work);
-	if (b->cpu != smp_processor_id()) {
-		printk(KERN_DEBUG "WQ on CPU%d, prefer CPU%d\n",
-		       smp_processor_id(), b->cpu);
-
-		if (!cpu_online(b->cpu)) {
-			cancel_delayed_work(&b->work);
-			return;
-		}
+	if (b->cpu != smp_processor_id() && !cpu_online(b->cpu)) {
+		cancel_delayed_work(&b->work);
+		return;
 	}
 	sync_buffer(b->cpu);
 
-- 
1.7.8.6


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