On Mon, Jan 5, 2015 at 5:45 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> On Thu, Nov 06, 2014 at 04:51:58PM +0000, Pawel Moll wrote:
>> Currently three clocks are implemented: CLOCK_REALITME = 0,
>> CLOCK_MONOTONIC = 1 and CLOCK_MONOTONIC_RAW = 2. The clock field is
>> 5 bits wide to allow for future extension to custom, non-POSIX clock
>> sources(MAX_CLOCK for those is 16, see include/uapi/linux/time.h) like
>> ARM CoreSight (hardware trace) timestamp generator.
>
>> @@ -304,7 +305,16 @@ struct perf_event_attr {
>> mmap2 : 1, /* include mmap with inode data */
>> comm_exec : 1, /* flag comm events that are due to an exec */
>> uevents : 1, /* allow uevents into the buffer */
>> - __reserved_1 : 38;
>> +
>> + /*
>> + * clock: one of the POSIX clock IDs:
>> + *
>> + * 0 - CLOCK_REALTIME
>> + * 1 - CLOCK_MONOTONIC
>> + * 4 - CLOCK_MONOTONIC_RAW
>> + */
>> + clock : 5, /* clock type */
>> + __reserved_1 : 33;
>>
>> union {
>> __u32 wakeup_events; /* wakeup every n events */
>
> This would put a constraint on actually changing MAX_CLOCKS, are the
> time people OK with that? Thomas, John?
Yea, I'd not want to enshrine MAX_CLOCKS if we can avoid it. We're
getting a bit close to it these days.
thanks
-john
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