On Mon, 5 Jun 2017, Anju T Sudhakar wrote:
static void thread_imc_mem_alloc(int cpu_id)It took me a while to understand that per_cpu_add is an array and not a new
{
- u64 ldbar_addr, ldbar_value;
int phys_id = topology_physical_package_id(cpu_id);
per_cpu_add[cpu_id] = (u64)alloc_pages_exact_nid(phys_id,
(size_t)IMC_THREAD_COUNTER_MEM, GFP_KERNEL | __GFP_ZERO);
fangled per cpu function which adds something to a per cpu variable.
So why is that storing the address as u64?
And why is this a NR_CPUS sized array instead of a regular per cpu variable?
+}So if that allocation fails then you happily proceed. Optmistic
+
+static void thread_imc_update_ldbar(unsigned int cpu_id)
+{
+ u64 ldbar_addr, ldbar_value;
+
+ if (per_cpu_add[cpu_id] == 0)
+ thread_imc_mem_alloc(cpu_id);
programming, right?
Yes. We did not add code to unregister the call back on failure.
+Ah, it's stored as u64 because you have to convert it back to a void
ldbar_addr = (u64)virt_to_phys((void *)per_cpu_add[cpu_id]);
pointer at the place where it is actually used. Interesting approach.
ldbar_value = (ldbar_addr & (u64)THREAD_IMC_LDBAR_MASK) |Just a general observation. If anything in init_imc_pmu() fails, then all
- (u64)THREAD_IMC_ENABLE;
+ (u64)THREAD_IMC_ENABLE;
mtspr(SPRN_LDBAR, ldbar_value);
}
@@ -442,6 +450,26 @@ static void core_imc_change_cpu_context(int old_cpu, int new_cpu)
perf_pmu_migrate_context(&core_imc_pmu->pmu, old_cpu, new_cpu);
}
+static int ppc_thread_imc_cpu_online(unsigned int cpu)
+{
+ thread_imc_update_ldbar(cpu);
+ return 0;
+}
+
+static int ppc_thread_imc_cpu_offline(unsigned int cpu)
+{
+ mtspr(SPRN_LDBAR, 0);
+ return 0;
+}
+
+void thread_imc_cpu_init(void)
+{
+ cpuhp_setup_state(CPUHP_AP_PERF_POWERPC_THREAD_IMC_ONLINE,
+ "perf/powerpc/imc_thread:online",
+ ppc_thread_imc_cpu_online,
+ ppc_thread_imc_cpu_offline);
+}
+
static int ppc_core_imc_cpu_online(unsigned int cpu)
{
const struct cpumask *l_cpumask;
@@ -953,6 +981,9 @@ int __init init_imc_pmu(struct imc_events *events, int idx,
if (ret)
return ret;
break;
+ case IMC_DOMAIN_THREAD:
+ thread_imc_cpu_init();
+ break;
default:
return -1; /* Unknown domain */
}
the hotplug callbacks are staying registered, at least I haven't seen
anything undoing it.
Thanks,
tglx