Hi Reinette, On 12/20/22 11:32, Reinette Chatre wrote: > 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? Its because of the way U-Bit tracking is implemented. The U-bit is tracked per RMID basis, not on a Per-Event + Per RMID basis. Therefore, resetting the U-Bit for 1 will reset it for both. This is what I got from h/w team. Thanks Babu > > Reinette > > -- Thanks Babu Moger
