Re: [PATCH -tip v2 2/6] perf bts: Introduce new sub command 'perf bts trace'

[Frederic Weisbecker <fweisbec@gmail.com>]

On Tue, Dec 21, 2010 at 08:56:23PM +0100, Peter Zijlstra wrote:
> On Tue, 2010-12-21 at 20:02 +0100, Frederic Weisbecker wrote:
> 
> > This could be a PERF_SAMPLE_RAW may be?
> 
> Well clearly not ;-)
> 
> But maybe we can do something like: PERF_RECORD_SAMPLES (note the
> plural):
> 
> struct {
> 	struct perf_event_header		header;
> 
> 	u64					nr;
> 	u32					common_type;
> 	u32					data_type;
> 
> 	struct perf_sample			common;
> 	struct perf_sample			data[nr];
> }
> 
> Where struct perf_sample is PERF_RECORD_SAMPLE without the
> perf_event_header bit.
> 
> Where we can split the many samples into a piece that is the same for
> all perf_samples::common, where the content specified by the
> PERF_SAMPLE_ bits from ::common_type, and the the rest lives in data[]
> specified by the PERF_SAMPLE_ bits from ::data_type.


Well, yeah but that involves some new corner cases in both the kernel
and userspace.

What about a generic branch record like:

struct branch {
	u64 nr;
	struct {
		u64 from;
		u64 to;
	}[nr]
}

This is going to be useful also when one day we'll
support the function tracer, lbr and so...