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SubjectRe: [tip:perf/core] perf/x86: Add generic Intel uncore PMU support
On 06/21/2012 03:43 PM, Andrew Morton wrote:
>
> Regardless of that, we have some head-scratching to do:
>
>
> #define UNCORE_PMU_HRTIMER_INTERVAL (60 * NSEC_PER_SEC)
>
> and
>
> #define NSEC_PER_SEC 1000000000L
>
> and 60 billion doesn't fit in 32 bits. So do we fix the
> perf_event_intel_uncore.c callsites? Or do we fix the
> UNCORE_PMU_HRTIMER_INTERVAL definition? Or do we fix the NSEC_PER_SEC
> definition?
>
> I'm thinking perhaps the latter. What *is* the type of a nanosecond in
> Linux? include/linux/ktime.h is pretty insistent that it is u64. If
> so, NSEC_PER_SEC should logically have type ULL. But changing both its
> size and signedness is a pretty big change.

We could change the size only. The range from 9223372036.854775808 to
18446744073.709551615 seconds (292-584 years) isn't really that significant.

-hpa


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