>-----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 unsigned int bm_threshold = BM_MAX_THRESHOLD; static >unsigned >> +int bm_mispred_evt_cnt; >> + >> +/* Branch monitoring counter owners */ static struct perf_event >> +*bm_counter_owner[2]; > >SNIP > >> + * Find a hardware counter for the target task >> + */ >> + for (i = 0; i < bm_num_counters; i++) { >> + if ((bm_counter_owner[i] == NULL) || >> + (bm_counter_owner[i]->state == >PERF_EVENT_STATE_DEAD)) { >> + counter_to_use = i; >> + bm_counter_owner[i] = event; >> + break; >> + } >> + } >> + >> + if (counter_to_use == -1) >> + return -EBUSY; > >not sure I understand, your docs says: "There are 2 8-bit counters that each.. >" > >so there are 2 counters per CPU? if that's corrent, isn't this check too strict >then? you could have more events configured running on other CPUs for >another tasks > >given that we do task only events here, should bm_counter_owner be part >of task, together with the limit..? I'm probably missing something..
Yes you are right. Initially, we had support for 2 events(from one or 2 tasks) to be monitored for the entire system. This indeed seems very limiting. In the next patchset, I will add support for 2 events per task (This is what the hardware can support). > >thanks, >jirka
