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cputime: Optimize jiffies_to_cputime(1)

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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 <[email protected]>
Acked-by: Peter Zijlstra <[email protected]>
Acked-by: Thomas Gleixner <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Stanislaw Gruszka 2009-07-29 12:15:29 +02:00 • committed by Ingo Molnar
commit a42548a188
8 changed files with 29 additions and 10 deletions
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4
kernel/itimer.c
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@ -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;