Messages in this thread Patch in this message | | | From | "Rafael J. Wysocki" <> | Date | Mon, 27 Mar 2023 18:37:32 +0200 | Subject | Re: [PATCH v3 13/24] thermal: intel: hfi: Store per-CPU IPCC scores |
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On Tue, Feb 7, 2023 at 6:02 AM Ricardo Neri <ricardo.neri-calderon@linux.intel.com> wrote: > > The scheduler reads the IPCC scores when balancing load. These reads can > be quite frequent. Hardware can also update the HFI table frequently. > Concurrent access may cause a lot of lock contention. It gets worse as the > number of CPUs increases. > > Instead, create separate per-CPU IPCC scores that the scheduler can read > without the HFI table lock. > > Cc: Ben Segall <bsegall@google.com> > Cc: Daniel Bristot de Oliveira <bristot@redhat.com> > Cc: Dietmar Eggemann <dietmar.eggemann@arm.com> > Cc: Ionela Voinescu <ionela.voinescu@arm.com> > Cc: Joel Fernandes (Google) <joel@joelfernandes.org> > Cc: Len Brown <len.brown@intel.com> > Cc: Lukasz Luba <lukasz.luba@arm.com> > Cc: Mel Gorman <mgorman@suse.de> > Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> > Cc: Steven Rostedt <rostedt@goodmis.org> > Cc: Tim C. Chen <tim.c.chen@intel.com> > Cc: Valentin Schneider <vschneid@redhat.com> > Cc: x86@kernel.org > Cc: linux-pm@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org> > Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> > --- > Changes since v2: > * Only create these per-CPU variables when Intel Thread Director is > supported. > > Changes since v1: > * Added this patch. > --- > drivers/thermal/intel/intel_hfi.c | 46 +++++++++++++++++++++++++++++++ > 1 file changed, 46 insertions(+) > > diff --git a/drivers/thermal/intel/intel_hfi.c b/drivers/thermal/intel/intel_hfi.c > index 2527ae3836c7..b06021828892 100644 > --- a/drivers/thermal/intel/intel_hfi.c > +++ b/drivers/thermal/intel/intel_hfi.c > @@ -29,6 +29,7 @@ > #include <linux/kernel.h> > #include <linux/math.h> > #include <linux/mutex.h> > +#include <linux/percpu.h> > #include <linux/percpu-defs.h> > #include <linux/printk.h> > #include <linux/processor.h> > @@ -170,6 +171,43 @@ static struct workqueue_struct *hfi_updates_wq; > #define HFI_UPDATE_INTERVAL HZ > #define HFI_MAX_THERM_NOTIFY_COUNT 16 > > +#ifdef CONFIG_IPC_CLASSES
It would be good to provide a (concise) description of this variable.
> +static int __percpu *hfi_ipcc_scores; > + > +static int alloc_hfi_ipcc_scores(void) > +{ > + if (!cpu_feature_enabled(X86_FEATURE_ITD)) > + return 0; > + > + hfi_ipcc_scores = __alloc_percpu(sizeof(*hfi_ipcc_scores) * > + hfi_features.nr_classes, > + sizeof(*hfi_ipcc_scores)); > + > + return !hfi_ipcc_scores;
I would do
if (!hfi_ipcc_scores) return -ENOMEM;
return 0;
Or make the function return bool.
> +} > + > +static void set_hfi_ipcc_score(void *caps, int cpu) > +{ > + int i, *hfi_class; > + > + if (!cpu_feature_enabled(X86_FEATURE_ITD)) > + return; > + > + hfi_class = per_cpu_ptr(hfi_ipcc_scores, cpu); > + > + for (i = 0; i < hfi_features.nr_classes; i++) { > + struct hfi_cpu_data *class_caps; > + > + class_caps = caps + i * hfi_features.class_stride; > + WRITE_ONCE(hfi_class[i], class_caps->perf_cap);
As it stands, it is unclear why WRITE_ONCE() is needed here.
> + } > +} > + > +#else > +static int alloc_hfi_ipcc_scores(void) { return 0; } > +static void set_hfi_ipcc_score(void *caps, int cpu) { } > +#endif /* CONFIG_IPC_CLASSES */ > + > static void get_hfi_caps(struct hfi_instance *hfi_instance, > struct thermal_genl_cpu_caps *cpu_caps) > { > @@ -192,6 +230,8 @@ static void get_hfi_caps(struct hfi_instance *hfi_instance, > cpu_caps[i].efficiency = caps->ee_cap << 2; > > ++i; > + > + set_hfi_ipcc_score(caps, cpu); > } > raw_spin_unlock_irq(&hfi_instance->table_lock); > } > @@ -580,8 +620,14 @@ void __init intel_hfi_init(void) > if (!hfi_updates_wq) > goto err_nomem; > > + if (alloc_hfi_ipcc_scores()) > + goto err_ipcc; > + > return; > > +err_ipcc: > + destroy_workqueue(hfi_updates_wq); > + > err_nomem: > for (j = 0; j < i; ++j) { > hfi_instance = &hfi_instances[j]; > --
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