Hi, Peter, > -----Original Message----- > From: Zhang, Rui > Sent: Monday, January 25, 2021 2:11 PM > To: 'Peter Zijlstra' <pet...@infradead.org> > Cc: 'mi...@redhat.com' <mi...@redhat.com>; 'a...@kernel.org' > <a...@kernel.org>; 'mark.rutl...@arm.com' <mark.rutl...@arm.com>; > 'alexander.shish...@linux.intel.com' <alexander.shish...@linux.intel.com>; > 'jo...@redhat.com' <jo...@redhat.com>; 'namhy...@kernel.org' > <namhy...@kernel.org>; 'linux-kernel@vger.kernel.org' <linux- > ker...@vger.kernel.org>; 'x...@kernel.org' <x...@kernel.org>; > 'kan.li...@linux.intel.com' <kan.li...@linux.intel.com>; > 'a...@linux.intel.com' > <a...@linux.intel.com> > Subject: RE: [PATCH 3/3] perf/x86/rapl: Fix psys-energy event on Intel SPR > platform > > Hi, Peter, > > > -----Original Message----- > > From: Zhang, Rui > > Sent: Sunday, January 17, 2021 10:34 PM > > To: 'Peter Zijlstra' <pet...@infradead.org> > > Cc: mi...@redhat.com; a...@kernel.org; mark.rutl...@arm.com; > > alexander.shish...@linux.intel.com; jo...@redhat.com; > > namhy...@kernel.org; linux-kernel@vger.kernel.org; x...@kernel.org; > > kan.li...@linux.intel.com; a...@linux.intel.com > > Subject: RE: [PATCH 3/3] perf/x86/rapl: Fix psys-energy event on Intel > > SPR platform > > > > Hi, Peter, > > > > > -----Original Message----- > > > From: Peter Zijlstra <pet...@infradead.org> > > > Sent: Saturday, January 16, 2021 8:50 PM > > > To: Zhang, Rui <rui.zh...@intel.com> > > > Cc: mi...@redhat.com; a...@kernel.org; mark.rutl...@arm.com; > > > alexander.shish...@linux.intel.com; jo...@redhat.com; > > > namhy...@kernel.org; linux-kernel@vger.kernel.org; x...@kernel.org; > > > kan.li...@linux.intel.com; a...@linux.intel.com > > > Subject: Re: [PATCH 3/3] perf/x86/rapl: Fix psys-energy event on > > > Intel SPR platform > > > Importance: High > > > > > > On Fri, Jan 15, 2021 at 05:22:08PM +0800, Zhang Rui wrote: > > > > There are several things special for the RAPL Psys energy counter, > > > > on Intel Sapphire Rapids platform. > > > > 1. it contains one Psys master package, and only CPUs on the master > > > > package can read valid value of the Psys energy counter, reading the > > > > MSR on CPUs in the slave package returns 0. > > > > 2. The master package does not have to be Physical package 0. And > when > > > > all the CPUs on the Psys master package are offlined, we lose the > > > > Psys > > > > energy counter, at runtime. > > > > 3. The Psys energy counter can be disabled by BIOS, while all the other > > > > energy counters are not affected. > > > > > > > > It is not easy to handle all of these in the current RAPL PMU > > > > design because > > > > a) perf_msr_probe() validates the MSR on some random CPU, which > > > > may > > > either > > > > be in the Psys master package or in the Psys slave package. > > > > b) all the RAPL events share the same PMU, and there is not API to > > remove > > > > the psys-energy event cleanly, without affecting the other events in > > > > the same PMU. > > > > > > > > This patch addresses the problems in a simple way. > > > > > > > > First, by setting .no_check bit for RAPL Psys MSR, the psys-energy > > > > event is always added, so we don't have to check the Psys > > > > ENERGY_STATUS MSR on master package. > > > > > > > > Then, rapl_not_visible() is removed because 1. it is useless for > > > > RAPL MSRs with .no_check cleared, because the > > > > .is_visible() callbacks is always overridden in perf_msr_probe(). > > > > 2. it is useless for RAPL MSRs with .no_check set, because we actually > > > > want the sysfs attributes always be visible for those MSRs. > > > > > > > > With the above changes, we always probe the psys-energy event on > > > > Intel SPR platform. Difference is that the event counter returns 0 > > > > when the Psys RAPL Domain is disabled by BIOS, or the Psys master > > > > package is > > > offlined. > > > > > > Maybe I'm too tired, but I cannot follow. How does this cure the > > > fact that the rapl_cpu_mask might not include that master thing. And > > > how can software detect what the master thing is to begin with? > > > > To make things simple, I ignore the master thing, and probe the > > psys-energy counter blindly on SPR. > > So rapl_cpu_mask still includes all the online CPUs. > > This means that psys-energy is "valid" on all packages, and it just > > returns different values on different packages. > > AKA, whole system power consumption on Psys master package, and Zero > > on Psys slave packages. > > > In short, the current code does not allow RAPL energy counter to return 0. > And all the work I do is to allow Psys energy counter to return 0. > In this way, the Psys event is "valid" on all CPUs, so we don't need to handle > the master thing. > The drawback is that we still see psys-energy event, but with 0 readout, > when Psys counter is not available (master package offlined, or psys > disabled). > > TBH, I'm not quite sure if I understand your original question correctly or > not, > so please let me know if there is still something unclear. > Sorry to bother, may I know your concern about this patch series?
Thanks, rui > Thanks, > rui > > > > Thanks, > > rui
