Re: [PATCH 2/6] perf: Support branch events logging

[Peter Zijlstra]

On Fri, Apr 14, 2023 at 03:47:29PM -0700, Andi Kleen wrote:

> > You really *must* make then a group such that perf knows what events to
> > associated with the LBR event and constain them to the 0-3 range of
> > PMCs.
> > 
> > If you want multiplexing, simply create multiple groups with an LBR
> > event in them.
> 
> 
> Well if you force groups then you require user space or a user which
> understands all the constraints

The LBR feature is naturally a group read, very similar to
PERF_SAMPLE_READ+PERF_FORMAT_GROUP.

> to create groups. I thought one of the basic ideas of perf was to be able to
> abstract those things.

Yeah, the abstraction at hand is a group.