Messages in this thread | | | Date | Tue, 20 Dec 2022 09:32:01 -0800 | Subject | Re: [PATCH v9 10/13] x86/resctrl: Add sysfs interface to write mbm_total_bytes_config | From | Reinette Chatre <> |
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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@intel.com> >> Sent: Thursday, December 15, 2022 12:25 PM >> To: Moger, Babu <Babu.Moger@amd.com>; corbet@lwn.net; >> tglx@linutronix.de; mingo@redhat.com; bp@alien8.de >> Cc: fenghua.yu@intel.com; dave.hansen@linux.intel.com; x86@kernel.org; >> hpa@zytor.com; paulmck@kernel.org; akpm@linux-foundation.org; >> quic_neeraju@quicinc.com; rdunlap@infradead.org; >> damien.lemoal@opensource.wdc.com; songmuchun@bytedance.com; >> peterz@infradead.org; jpoimboe@kernel.org; pbonzini@redhat.com; >> chang.seok.bae@intel.com; pawan.kumar.gupta@linux.intel.com; >> jmattson@google.com; daniel.sneddon@linux.intel.com; Das1, Sandipan >> <Sandipan.Das@amd.com>; tony.luck@intel.com; james.morse@arm.com; >> linux-doc@vger.kernel.org; linux-kernel@vger.kernel.org; >> bagasdotme@gmail.com; eranian@google.com; christophe.leroy@csgroup.eu; >> jarkko@kernel.org; adrian.hunter@intel.com; quic_jiles@quicinc.com; >> peternewman@google.com >> 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
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