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authorStanislaw Gruszka <sgruszka@redhat.com>2009-07-29 12:15:29 +0200
committerIngo Molnar <mingo@elte.hu>2009-08-03 14:48:36 +0200
commita42548a18866e87092db93b771e6c5b060d78401 (patch)
tree897acf5794920ec9c6fd7f87af63908d0c1988f9 /kernel/posix-cpu-timers.c
parentd1e3b6d195770bd422e3229b88edfc154b6a27dd (diff)
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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>
Diffstat (limited to 'kernel/posix-cpu-timers.c')
-rw-r--r--kernel/posix-cpu-timers.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 69c92374355..18bdde6f676 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -1086,7 +1086,7 @@ static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
it->error += it->incr_error;
if (it->error >= onecputick) {
it->expires = cputime_sub(it->expires,
- jiffies_to_cputime(1));
+ cputime_one_jiffy);
it->error -= onecputick;
}
} else
@@ -1461,7 +1461,7 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
if (!cputime_eq(*oldval, cputime_zero)) {
if (cputime_le(*oldval, now.cpu)) {
/* Just about to fire. */
- *oldval = jiffies_to_cputime(1);
+ *oldval = cputime_one_jiffy;
} else {
*oldval = cputime_sub(*oldval, now.cpu);
}
@@ -1712,7 +1712,7 @@ static __init int init_posix_cpu_timers(void)
register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
- cputime_to_timespec(jiffies_to_cputime(1), &ts);
+ cputime_to_timespec(cputime_one_jiffy, &ts);
onecputick = ts.tv_nsec;
WARN_ON(ts.tv_sec != 0);