On Wed, 29 Jul 2015, Peter Zijlstra wrote:
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.
Cpu_online was just good enough as the tasks would be ready to be scheduled. iow
, its just at the right time.
could avoid using the interrupt disabled time ?
Dont really need the *interrupt disabled* cpu_starting notification - can leave
that for more important code/lock free code can go there. or this change should
not be a big concern ?
+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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