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, 2 insertions, 2 deletions

diff --git a/kernel/itimer.c b/kernel/itimer.c
index 21adff7b2a17..8078a32d3b10 100644
--- a/kernel/itimer.c
+++ b/kernel/itimer.c
@@ -64,7 +64,7 @@ static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
 
                 if (cputime_le(cval, t))
                         /* about to fire */
-                        cval = jiffies_to_cputime(1);
+                        cval = cputime_one_jiffy;
                 else
                         cval = cputime_sub(cval, t);
         }
@@ -161,7 +161,7 @@ static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
         if (!cputime_eq(cval, cputime_zero) ||
             !cputime_eq(nval, cputime_zero)) {
                 if (cputime_gt(nval, cputime_zero))
-                        nval = cputime_add(nval, jiffies_to_cputime(1));
+                        nval = cputime_add(nval, cputime_one_jiffy);
                 set_process_cpu_timer(tsk, clock_id, &nval, &cval);
         }
         it->expires = nval;