Messages in this thread | | | Subject | Re: [PATCH 1/2] perf tools: Add reference timestamp to perf header | From | Peter Zijlstra <> | Date | Mon, 13 Dec 2010 18:35:16 +0100 |
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On Mon, 2010-12-13 at 15:22 -0200, Arnaldo Carvalho de Melo wrote: > > No, the last one already happened, you cannot postpone the last one, > > there will always be another excuse. > > Did you understand the use case? How to have multiple reference times > when appending?
Yes, I understood it perfectly, I just detest the existence of these pure user records, they need to die ASAP.
> "last one" means adding a multiplexor, PERF_RECORD_LAST_ONE if you will, > and inside it we add new events if the need arises. Then never again we > add a PERF_RECORD_ event in userspace.
Nah, that sucks too, the whole concept of pure user-space events in that stream sucks.
There's multiple things you can do, you could:
- create a kernel event PERF_RECORD_NEW_BUFFER and stuff that into each fresh buffer when its created, it could contain all kinds of 1-time information, like: * this CLOCK_MONOTONIC offset (for what little good that does, since our clock isn't strictly sync'ed to CLOCK_MONOTONIC so we can incur arbitrary drift). * architecture details, like 64/32 host info needed for the PERF_SAMPLE_REGS stuff.
- extend the existing header infrastructure to write a new header in front of the new stream. The main header already has a data section that points to the end of the stream, add a continuation header section that points to a continuation-header used to appends and record the clock offset data in there.
- something else entirely.
Just stop using these stupid fake events and be somewhat creative.
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