Re: [PATCH 3/6] perf record: add time-of-day option

Peter Zijlstra
2011-03-01T15:33:49Z

On Tue, 2011-03-01 at 07:35 -0700, David Ahern wrote:
>
> On 03/01/2011 07:29 AM, Peter Zijlstra wrote:
>
> >> +/* add a sample to the event stream based on user request */
> >> +static int perf_event_generate_sample(struct perf_event *event)
> >> +{
> >> + struct perf_sample_data data;
> >> + struct pt_regs regs;
> >> +
> >> + perf_fetch_caller_regs(&regs);
> >> + event->pmu->read(event);
> >> + perf_sample_data_init(&data, 0);
> >> + data.period = event->hw.last_period;
> >> + perf_event_output(event, 0, &data, &regs);
> >> +
> >> + return 0;
> >> +}
> >
> > I'm not quite sure why you need this..
> >
>
> periodic samples are generated after the specified period. I want the
> first sample immediately and the remainder based on the set period.
>
> So generically, how do you get the first sample into the event stream
> and let the others happen based on the timer? I need not only the
> counter value but also the perf_clock timestamp that comes from the
> SAMPLE_TIME attribute.

Again, why?