>-----Original Message----- >From: Jiri Olsa [mailto:jolsa@xxxxxxxxxx] >Sent: Saturday, November 4, 2017 6:26 AM >To: Megha Dey <megha.dey@xxxxxxxxxxxxxxx> >Cc: x86@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux- >doc@xxxxxxxxxxxxxxx; tglx@xxxxxxxxxxxxx; mingo@xxxxxxxxxx; >hpa@xxxxxxxxx; andriy.shevchenko@xxxxxxxxxxxxxxx; >kstewart@xxxxxxxxxxxxxxxxxxx; Yu, Yu-cheng <yu-cheng.yu@xxxxxxxxx>; >Brown, Len <len.brown@xxxxxxxxx>; gregkh@xxxxxxxxxxxxxxxxxxx; >peterz@xxxxxxxxxxxxx; acme@xxxxxxxxxx; >alexander.shishkin@xxxxxxxxxxxxxxx; namhyung@xxxxxxxxxx; >vikas.shivappa@xxxxxxxxxxxxxxx; pombredanne@xxxxxxxx; >me@xxxxxxxxxxxx; bp@xxxxxxx; Andrejczuk, Grzegorz ><grzegorz.andrejczuk@xxxxxxxxx>; Luck, Tony <tony.luck@xxxxxxxxx>; >corbet@xxxxxxx; Shankar, Ravi V <ravi.v.shankar@xxxxxxxxx>; Dey, Megha ><megha.dey@xxxxxxxxx> >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 -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
