[RFD PATCH 1/4] powerpc: cpu: Reduce the polling interval in__cpu_up()

From: Gautham R Shenoy
Date: Tue Jun 16 2009 - 01:39:27 EST

The cpu online operation on a powerpc today takes order of 200-220ms. Of
this time, approximately 200ms is taken up by __cpu_up(). This is because
we poll every 200ms to check if the new cpu has notified it's presence
through the cpu_callin_map. We poll every 200ms until the new cpu sets
the value in cpu_callin_map or 5 seconds elapse, whichever comes earlier.

However, the time taken by the new processor to indicate it's presence has
found to be less than a millisecond. Keeping this in mind, reduce the
polling interval from 200ms to 1ms while retaining the 5 second timeout.

Signed-off-by: Gautham R Shenoy <ego@xxxxxxxxxx>
arch/powerpc/kernel/smp.c | 5 ++---
1 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 65484b2..00c13a1 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -411,9 +411,8 @@ int __cpuinit __cpu_up(unsigned int cpu)
* CPUs can take much longer to come up in the
* hotplug case. Wait five seconds.
- for (c = 25; c && !cpu_callin_map[cpu]; c--) {
- msleep(200);
- }
+ for (c = 5000; c && !cpu_callin_map[cpu]; c--)
+ msleep(1);

if (!cpu_callin_map[cpu]) {

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