>-----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
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