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


On 03/01/2011 09:00 AM, Peter Zijlstra wrote:
> On Tue, 2011-03-01 at 08:41 -0700, David Ahern wrote:
>
>> realtime-clock counter is created with a period N. How do you correlate
>> perf_clock to time-of-day until now + N?
>
> You scan fwd? Since its at most N time ahead you're scanning fwd its
> still constant time.

So I potentially scan a multi-gigabyte file looking for a single event
-- that may not even exist. From a usability perspective the time string
should appear if the clock event exists and not if it does not exist.
This should happen automatically.

>
> Thing is, I'm really not convinced this is a very useful ioctl() in
> generic, and ioctl()s really need a good justification to add.
>

I did not code it create samples of a realtime-clock event; I coded it
to add an event to the stream on demand -- whatever event the fd is tied to.

David


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