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

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Message-ID: <4D6D0438.2090901@cisco.com>
Date:	Tue, 01 Mar 2011 07:35:36 -0700
From:	David Ahern <daahern@...co.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	acme@...stprotocols.net, mingo@...e.hu, fweisbec@...il.com,
	paulus@...ba.org, tglx@...utronix.de
Subject: Re: [PATCH 3/6] perf record: add time-of-day option



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.

David

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