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, 0 deletions

diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index eae4511ceeac..211d7b0cd370 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -193,6 +193,8 @@ EXPORT_SYMBOL(__cputime_clockt_factor);
 DEFINE_PER_CPU(unsigned long, cputime_last_delta);
 DEFINE_PER_CPU(unsigned long, cputime_scaled_last_delta);
 
+cputime_t cputime_one_jiffy;
+
 static void calc_cputime_factors(void)
 {
         struct div_result res;
@@ -500,6 +502,7 @@ static int __init iSeries_tb_recal(void)
                                 tb_to_xs = divres.result_low;
                                 vdso_data->tb_ticks_per_sec = tb_ticks_per_sec;
                                 vdso_data->tb_to_xs = tb_to_xs;
+                                setup_cputime_one_jiffy();
                         }
                         else {
                                 printk( "Titan recalibrate: FAILED (difference > 4 percent)\n"
@@ -945,6 +948,7 @@ void __init time_init(void)
         tb_ticks_per_usec = ppc_tb_freq / 1000000;
         tb_to_us = mulhwu_scale_factor(ppc_tb_freq, 1000000);
         calc_cputime_factors();
+        setup_cputime_one_jiffy();
 
         /*
          * Calculate the length of each tick in ns.  It will not be