Re: [tip:perf/core] perf/x86: Add generic Intel uncore PMU support

["H. Peter Anvin" <hpa@xxxxxxxxx>]

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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