lk/linux-kernel-test
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

cputime: Optimize jiffies_to_cputime(1)

Browse Source 
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>
This commit is contained in:
Stanislaw Gruszka
2009-07-29 12:15:29 +02:00
committed by Ingo Molnar
parent d1e3b6d195
commit a42548a188
8 changed files with 29 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
kernel/itimer.c
View File

@@ -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;