>-----Original Message----- >From: Jiri Olsa [mailto:[email protected]] >Sent: Saturday, November 4, 2017 6:26 AM >To: Megha Dey <[email protected]> >Cc: [email protected]; [email protected]; linux- >[email protected]; [email protected]; [email protected]; >[email protected]; [email protected]; >[email protected]; Yu, Yu-cheng <[email protected]>; >Brown, Len <[email protected]>; [email protected]; >[email protected]; [email protected]; >[email protected]; [email protected]; >[email protected]; [email protected]; >[email protected]; [email protected]; Andrejczuk, Grzegorz ><[email protected]>; Luck, Tony <[email protected]>; >[email protected]; Shankar, Ravi V <[email protected]>; Dey, Megha ><[email protected]> >Subject: Re: [PATCH V0 2/3] perf/x86/intel/bm.c: Add Intel Branch >Monitoring support > >On Fri, Nov 03, 2017 at 11:00:05AM -0700, Megha Dey wrote: > >SNIP > >> + >> +static void intel_bm_event_update(struct perf_event *event) { >> + union bm_detect_status cur_stat; >> + >> + rdmsrl(BR_DETECT_STATUS_MSR, cur_stat.raw); >> + local64_set(&event->hw.prev_count, (uint64_t)cur_stat.raw); } >> + >> +static void intel_bm_event_stop(struct perf_event *event, int mode) { >> + wrmsrl(BR_DETECT_COUNTER_CONFIG_BASE + event->id, >> + (event->hw.bm_counter_conf & ~1)); >> + >> + intel_bm_event_update(event); >> +} >> + >> +static void intel_bm_event_del(struct perf_event *event, int flags) { >> + intel_bm_event_stop(event, flags); >> +} >> + >> +static void intel_bm_event_read(struct perf_event *event) { } > >should you call intel_bm_event_update in here? so the read syscall gets >updated data in case the case the event is active
We do not update the event->count in the intel_bm_event_update function. We are basically saving the status register contents when a task is being scheduled out. So it has nothing to do with the read syscall. Having said that, I will probably put what stop() does in del() and get rid of the stop() function. > >jirka
