Messages in this thread | | | Date | Wed, 29 Jul 2015 17:53:02 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 8/9] x86/intel_rdt: Hot cpu support for Cache Allocation |
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On Wed, Jul 01, 2015 at 03:21:09PM -0700, Vikas Shivappa wrote: > +/* > + * cbm_update_msrs() - Updates all the existing IA32_L3_MASK_n MSRs > + * which are one per CLOSid except IA32_L3_MASK_0 on the current package. > + */ > +static void cbm_update_msrs(void *info) > +{ > + int maxid = boot_cpu_data.x86_cache_max_closid; > + unsigned int i; > + > + /* > + * At cpureset, all bits of IA32_L3_MASK_n are set. > + * The index starts from one as there is no need > + * to update IA32_L3_MASK_0 as it belongs to root cgroup > + * whose cache mask is all 1s always. > + */ > + for (i = 1; i < maxid; i++) { > + if (ccmap[i].clos_refcnt) > + cbm_cpu_update((void *)i); > + } > +} > + > +static inline void intel_rdt_cpu_start(int cpu) > +{ > + struct intel_pqr_state *state = &per_cpu(pqr_state, cpu); > + > + state->closid = 0; > + mutex_lock(&rdt_group_mutex); > + if (rdt_cpumask_update(cpu)) > + smp_call_function_single(cpu, cbm_update_msrs, NULL, 1); > + mutex_unlock(&rdt_group_mutex); > +}
If you were to guard your array with both a mutex and a raw_spinlock then you can avoid the IPI and use CPU_STARTING.
> +static int intel_rdt_cpu_notifier(struct notifier_block *nb, > + unsigned long action, void *hcpu) > +{ > + unsigned int cpu = (unsigned long)hcpu; > + > + switch (action) { > + case CPU_DOWN_FAILED: > + case CPU_ONLINE: > + intel_rdt_cpu_start(cpu); > + break; > + case CPU_DOWN_PREPARE: > + intel_rdt_cpu_exit(cpu); > + break; > + default: > + break; > + } > + > + return NOTIFY_OK; > }
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