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SubjectRe: [PATCH resend5 4/4] cputime: optimize jiffies_to_cputime(1)
Hi.

> > This patch (with 3 previous) was compiled on x86, x86_64, ppc with
> > CONFIG_VIRT_CPU_ACCOUNTNG=n, ppc64 with CONFIG_VIRT_CPU_ACCOUNTING=y.
> > Run time testing was done only on x86.

I tested patches on ppc64 with CONFIG_VIRT_CPU_ACCOUNTING=y . Additionally I
measure impact of iffies_to_cputime(1) to cputime_one_jiffiy conversion on
check_cpu_itimer() calls with below code:

+ xstart = get_cycles();
+ barrier();
check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF], &prof_expires, ptime,
SIGPROF);
check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime,
SIGVTALRM);
+ barrier();
+ xend = get_cycles();
+ check_cpu_itimer_cycles += xend - xstart;
+ check_cpu_itimer_n++;

Using cputime_one_jiffy was about 4% faster.

Cheers
Stanislaw


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