* Paolo Bonzini (pbonz...@redhat.com) wrote: > On 17/03/2016 17:29, Dr. David Alan Gilbert wrote: > > OK, so I see TraceEvent has a TraceEventID field; so yes that works easily; > > it turns out to be a little more expensive though since what was a: > > > > trace_events_dstate[id] > > > > is now > > trace_events_dstate[te->id] > > That however makes you waste a lot of cache on trace_events_dstate > (commit 585ec72, "trace: track enabled events in a separate array", > 2016-02-03). > > Perhaps we get the linker to do compute the id, for example by using a > separate data section and then use te-&te_first to compute the id... > Richard, do you have ideas on how to do this in a reasonably portable > manner?
It's possible we don't need the unique-id on the fast-path; for example if we had an id that was only unique within each trace-events file, and it's own trace_events_dstate[] that used that ID, then that would still be a nice statically known id. You'd still need to be able to get the global ID for the simple-event and anything else that needed it. > > But hang on, what's the 'sstate' in TraceEvent; do we actually need two > > state fields if we're passing a TraceEvent pointer around? > > sstate means the event is unavailable, it's basically just a way to > provide better error messages. Dave > > Paolo -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
