cputime: Optimize jiffies_to_cputime(1)

For powerpc with CONFIG_VIRT_CPU_ACCOUNTING
jiffies_to_cputime(1) is not compile time constant and run time
calculations are quite expensive. To optimize we use
precomputed value. For all other architectures is is
preprocessor definition.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
LKML-Reference: <1248862529-6063-5-git-send-email-sgruszka@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 4 insertions, 5 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 1b59e265273b..8f977d5cc515 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5031,17 +5031,16 @@ void account_idle_time(cputime_t cputime)
  */
 void account_process_tick(struct task_struct *p, int user_tick)
 {
-        cputime_t one_jiffy = jiffies_to_cputime(1);
-        cputime_t one_jiffy_scaled = cputime_to_scaled(one_jiffy);
+        cputime_t one_jiffy_scaled = cputime_to_scaled(cputime_one_jiffy);
         struct rq *rq = this_rq();
 
         if (user_tick)
-                account_user_time(p, one_jiffy, one_jiffy_scaled);
+                account_user_time(p, cputime_one_jiffy, one_jiffy_scaled);
         else if ((p != rq->idle) || (irq_count() != HARDIRQ_OFFSET))
-                account_system_time(p, HARDIRQ_OFFSET, one_jiffy,
+                account_system_time(p, HARDIRQ_OFFSET, cputime_one_jiffy,
                                     one_jiffy_scaled);
         else
-                account_idle_time(one_jiffy);
+                account_idle_time(cputime_one_jiffy);
 }
 
 /*