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

[Andi Kleen]

On 4/17/2023 4:46 AM, Peter Zijlstra wrote:
> On Fri, Apr 14, 2023 at 03:47:29PM -0700, Andi Kleen wrote:
> > > Yeah, don't do this. There is no guarantee what so ever you'll get any
> > > of those events in the 0-3 range.
> >
> > The kernel can simply force to 0-3 if LBR is enabled and the feature too.
> > It's in Kan's patch
> >
> > and it isn't particularly complicated.
> And what, totally leave 4-7 unused even if those counters were not
> related to LBR at all? That seems exceedingly daft.


Only for the events which enabled LBR and also only if the branch events 
feature is enabled

-j event -e '{event1:b,event2:b,event3:b,event4:b,event5,event6}'

event5 and 6 can go > 3

Given there is currently no syntax to control branch events inside a 
group other than fully enabling/disabling LBR.

Kan, I guess that could be added to the user tools.

-Andi