Re: [PATCH v5 13/17] perf: Support deferred user callchains

On Fri, 9 May 2025 08:45:46 -0700
Namhyung Kim <[email protected]> wrote:

> > Is it possible to have many threads writing into the same
> > ring buffer in that scenario ? Are all event records stamped
> > with their associated PID ? As long as we have enough information
> > to know which thread was associated with the timestamp cookie
> > on both ends (request for callchain and saving the user callchain
> > on return to userspace), we should be OK.  
> 
> Yep, basically perf sets PERF_SAMPLE_TID (and sample_id_all) which makes
> every records come with PID/TID.. 

If LTTng is fine with this too, then we should be OK as perf and ftrace
both record TID in the events. I'm assuming that BPF would be OK too.

-- Steve