Hi Babu, On 12/19/2022 11:28 AM, Moger, Babu wrote: > [AMD Official Use Only - General] > > Hi Reinette, > >> -----Original Message----- >> From: Reinette Chatre <reinette.chatre@xxxxxxxxx> >> Sent: Thursday, December 15, 2022 12:25 PM >> To: Moger, Babu <Babu.Moger@xxxxxxx>; corbet@xxxxxxx; >> tglx@xxxxxxxxxxxxx; mingo@xxxxxxxxxx; bp@xxxxxxxxx >> Cc: fenghua.yu@xxxxxxxxx; dave.hansen@xxxxxxxxxxxxxxx; x86@xxxxxxxxxx; >> hpa@xxxxxxxxx; paulmck@xxxxxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx; >> quic_neeraju@xxxxxxxxxxx; rdunlap@xxxxxxxxxxxxx; >> damien.lemoal@xxxxxxxxxxxxxxxxxx; songmuchun@xxxxxxxxxxxxx; >> peterz@xxxxxxxxxxxxx; jpoimboe@xxxxxxxxxx; pbonzini@xxxxxxxxxx; >> chang.seok.bae@xxxxxxxxx; pawan.kumar.gupta@xxxxxxxxxxxxxxx; >> jmattson@xxxxxxxxxx; daniel.sneddon@xxxxxxxxxxxxxxx; Das1, Sandipan >> <Sandipan.Das@xxxxxxx>; tony.luck@xxxxxxxxx; james.morse@xxxxxxx; >> linux-doc@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; >> bagasdotme@xxxxxxxxx; eranian@xxxxxxxxxx; christophe.leroy@xxxxxxxxxx; >> jarkko@xxxxxxxxxx; adrian.hunter@xxxxxxxxx; quic_jiles@xxxxxxxxxxx; >> peternewman@xxxxxxxxxx >> Subject: Re: [PATCH v9 10/13] x86/resctrl: Add sysfs interface to write >> mbm_total_bytes_config >> >> Hi Babu, >> >> On 12/1/2022 7:37 AM, Babu Moger wrote: ... >>> + /* >>> + * When an Event Configuration is changed, the bandwidth counters >>> + * for all RMIDs and Events will be cleared by the hardware. The >>> + * hardware also sets MSR_IA32_QM_CTR.Unavailable (bit 62) for >>> + * every RMID on the next read to any event for every RMID. >>> + * Subsequent reads will have MSR_IA32_QM_CTR.Unavailable (bit 62) >>> + * cleared while it is tracked by the hardware. Clear the >>> + * mbm_local and mbm_total counts for all the RMIDs. >>> + */ >>> + resctrl_arch_reset_rmid_all(r, d); >> >> If I understand correctly the expectation is that when user space read counters >> (via mon_data files) right after the configuration was changed then this read >> will return "Unavailable" and then the next read will return data. >> >> If this is the case then I think a snippet about this user experience would be >> helpful to add to the documentation. > > Ok. How about this in the documentation? > > "When an event configuration is changed, the bandwidth counters for all the RMIDs and the events will be cleared for that domain. > The next read for every RMID will report "Unavailable" and subsequent reads will report the valid value." > > Thinking about this more ... why are the counters for all eventids cleared when only one eventid's configuration is changed? Reinette
