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s390/time: use stck clock fast for do_account_vtime

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The last high frequency call site of the STCK instruction is
do_account_vtime. Replace it with the faster STCKF instruction.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky 2014-10-20 10:24:39 +02:00
parent cac7f24298
commit 1f759bb3a2
1 changed files with 4 additions and 0 deletions
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arch/s390/kernel/vtime.c
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@ -66,7 +66,11 @@ static int do_account_vtime(struct task_struct *tsk, int hardirq_offset)
clock = S390_lowcore.last_update_clock;
asm volatile(
" stpt %0\n" /* Store current cpu timer value */
#ifdef CONFIG_HAVE_MARCH_Z9_109_FEATURES
" stckf %1" /* Store current tod clock value */
#else
" stck %1" /* Store current tod clock value */
#endif
: "=m" (S390_lowcore.last_update_timer),
"=m" (S390_lowcore.last_update_clock));
S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;