Messages in this thread | | | Subject | Re: [RFC 2/2] perf: Marker software event and ioctl | From | Pawel Moll <> | Date | Tue, 16 Sep 2014 17:37:43 +0100 |
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On Tue, 2014-09-16 at 08:44 +0100, Ingo Molnar wrote: > I think adding an ioctl to inject user-provided data into the > event stream is sensible, as long as there's a separate 'user > generated data' event for it, etc. > > The main usecase I could see would be to introduce a > perf_printf() variant, supported by 'perf trace' by default, to > add various tracable printouts to apps. > > Timestamps generated by apps would be another usecase. It would > probably be wise to add a 32-bit (or 64-bit) message type ID, > plus a length field, with a message type registry somewhere in > tools/perf/ (and reference implementation for each new subtype), > to keep things organized yet flexible going forward.
Right, so this is pretty much what I got talking to Arnaldo...
> { u64 type; /* 0 means zero-terminated string in data */ > u32 size; > char data[size]; } && PERF_SAMPLE_MARKER
... with one type - 0 - defined as a "universal" string (so any possible tool knows what to do about it), the rest being left to userspace (this "registry" you mention).
Before I proceed any further, is the term "marker" acceptable? Maybe a "printf" instead? Or a "log"? As we know naming is often single most discussed subject when it comes to new things in the kernel ;-)
Pawel
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