Xen devel - Aug 2006 - [PATCH] Use macro to walk through online cpus

There are two cases that I know of in xen/common where we waste cycles
walking through a list from zero to NR_CPUS.  This patch makes them use
for_each_online_cpu instead.

Signed-off-by: Amos Waterland <apw@us.ibm.com>

---

 schedule.c |    2 +-
 timer.c    |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff -r 326e6736d92b xen/common/schedule.c
--- a/xen/common/schedule.c	Mon Aug 21 10:04:37 2006 -0400
+++ b/xen/common/schedule.c	Mon Aug 21 22:31:12 2006 -0400
@@ -633,7 +633,7 @@ void __init scheduler_init(void)
 
     open_softirq(SCHEDULE_SOFTIRQ, __enter_scheduler);
 
-    for ( i = 0; i < NR_CPUS; i++ )
+    for_each_online_cpu( i )
     {
         spin_lock_init(&per_cpu(schedule_data, i).schedule_lock);
         init_timer(&per_cpu(schedule_data, i).s_timer, s_timer_fn, NULL,
i);
diff -r 326e6736d92b xen/common/timer.c
--- a/xen/common/timer.c	Mon Aug 21 10:04:37 2006 -0400
+++ b/xen/common/timer.c	Mon Aug 21 22:31:21 2006 -0400
@@ -382,7 +382,7 @@ void __init timer_init(void)
     SET_HEAP_SIZE(&dummy_heap, 0);
     SET_HEAP_LIMIT(&dummy_heap, 0);
 
-    for ( i = 0; i < NR_CPUS; i++ )
+    for_each_online_cpu( i )
     {
         spin_lock_init(&per_cpu(timers, i).lock);
         per_cpu(timers, i).heap = &dummy_heap;

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On 22/8/06 4:12 am, "Amos Waterland" <apw@us.ibm.com> wrote:
> There are two cases that I know of in xen/common where we waste cycles
> walking through a list from zero to NR_CPUS.  This patch makes them use
> for_each_online_cpu instead.
> 
> Signed-off-by: Amos Waterland <apw@us.ibm.com>
Better to use for_each_cpu() in case any arch supports CPU hotplug in
future. The wasted cycles are unimportant since these loops run only once,
at boot time.

 -- Keir



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