Re: idle issues running sembench on 128 cpus II

From: Dave Kleikamp
Date: Thu May 05 2011 - 11:26:02 EST


On 05/04/2011 06:48 PM, Andi Kleen wrote:
Here's a new patch without the raw. Boots on my Westmere.

Sorry appended the old patch. Here's really the new version.

From: Andi Kleen<ak@xxxxxxxxxxxxxxx>
Date: Wed, 4 May 2011 15:09:27 -0700
Subject: [PATCH] Move C3 stop test outside lock

Avoid taking locks in the idle path for systems where the timer
doesn't stop in C3.

Signed-off-by: Andi Kleen<ak@xxxxxxxxxxxxxxx>

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index da800ff..7f565b7 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -456,23 +456,22 @@ void tick_broadcast_oneshot_control(unsigned long reason)
unsigned long flags;
int cpu;

- raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
-
/*
* Periodic mode does not care about the enter/exit of power
* states
*/
if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
- goto out;
+ return;

- bc = tick_broadcast_device.evtdev;
cpu = smp_processor_id();
+ bc = tick_broadcast_device.evtdev;
td =&per_cpu(tick_cpu_device, cpu);
dev = td->evtdev;

if (!(dev->features& CLOCK_EVT_FEAT_C3STOP))
- goto out;
+ return;

out: is now defined but not used in this function.


+ raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) {
if (!cpumask_test_cpu(cpu, tick_get_broadcast_oneshot_mask())) {
cpumask_set_cpu(cpu, tick_get_broadcast_oneshot_mask());

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