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x86/perf/intel/cstate: Make cstate hotplug handling actually work

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The current implementation aside of being an incomprehensible mess is broken.

  # cat /sys/bus/event_source/devices/cstate_core/cpumask
  0-17

That's on a quad socket machine with 72 physical cores! Qualitee stuff.

So it's not a surprise that event migration in case of CPU hotplug does not
work either.

  # perf stat -e cstate_core/c6-residency/ -C 1 sleep 60 &
  # echo 0 >/sys/devices/system/cpu/cpu1/online

Tracing cstate_pmu_event_update gives me:

 [001] cstate_pmu_event_update <-event_sched_out

After the fix it properly moves the event:

 [001] cstate_pmu_event_update <-event_sched_out
 [073] cstate_pmu_event_update <-__perf_event_read
 [073] cstate_pmu_event_update <-event_sched_out

The migration of pkg events does not work either. Not that I'm surprised.

I really could not be bothered to decode that loop mess and simply replaced it
by querying the proper cpumasks which give us the answer in a comprehensible
way.

This also requires to direct the event to the current active reader CPU in
cstate_pmu_event_init() otherwise the hotplug logic can't work.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[ Added event->cpu < 0 test to not explode]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/20160320185623.422519970@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Thomas Gleixner 2016-03-20 18:59:02 +00:00 committed by Ingo Molnar
parent 4b6e2571bf
commit 49de0493e5
1 changed files with 51 additions and 67 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

118
arch/x86/events/intel/cstate.c
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@ -385,7 +385,7 @@ static ssize_t cstate_get_attr_cpumask(struct device *dev,
static int cstate_pmu_event_init(struct perf_event *event)
{
u64 cfg = event->attr.config;
int ret = 0;
int cpu;
if (event->attr.type != event->pmu->type)
return -ENOENT;
@ -400,26 +400,36 @@ static int cstate_pmu_event_init(struct perf_event *event)
event->attr.sample_period) /* no sampling */
return -EINVAL;
if (event->cpu < 0)
return -EINVAL;
if (event->pmu == &cstate_core_pmu) {
if (cfg >= PERF_CSTATE_CORE_EVENT_MAX)
return -EINVAL;
if (!core_msr[cfg].attr)
return -EINVAL;
event->hw.event_base = core_msr[cfg].msr;
cpu = cpumask_any_and(&cstate_core_cpu_mask,
topology_sibling_cpumask(event->cpu));
} else if (event->pmu == &cstate_pkg_pmu) {
if (cfg >= PERF_CSTATE_PKG_EVENT_MAX)
return -EINVAL;
if (!pkg_msr[cfg].attr)
return -EINVAL;
event->hw.event_base = pkg_msr[cfg].msr;
} else
cpu = cpumask_any_and(&cstate_pkg_cpu_mask,
topology_core_cpumask(event->cpu));
} else {
return -ENOENT;
}
/* must be done before validate_group */
if (cpu >= nr_cpu_ids)
return -ENODEV;
event->cpu = cpu;
event->hw.config = cfg;
event->hw.idx = -1;
return ret;
return 0;
}
static inline u64 cstate_pmu_read_counter(struct perf_event *event)
@ -469,102 +479,76 @@ static int cstate_pmu_event_add(struct perf_event *event, int mode)
return 0;
}
/*
* Check if exiting cpu is the designated reader. If so migrate the
* events when there is a valid target available
*/
static void cstate_cpu_exit(int cpu)
{
int i, id, target;
unsigned int target;
/* cpu exit for cstate core */
if (has_cstate_core) {
id = topology_core_id(cpu);
target = -1;
if (has_cstate_core &&
cpumask_test_and_clear_cpu(cpu, &cstate_core_cpu_mask)) {
for_each_online_cpu(i) {
if (i == cpu)
continue;
if (id == topology_core_id(i)) {
target = i;
break;
}
}
if (cpumask_test_and_clear_cpu(cpu, &cstate_core_cpu_mask) && target >= 0)
target = cpumask_any_but(topology_sibling_cpumask(cpu), cpu);
/* Migrate events if there is a valid target */
if (target < nr_cpu_ids) {
cpumask_set_cpu(target, &cstate_core_cpu_mask);
WARN_ON(cpumask_empty(&cstate_core_cpu_mask));
if (target >= 0)
perf_pmu_migrate_context(&cstate_core_pmu, cpu, target);
}
}
/* cpu exit for cstate pkg */
if (has_cstate_pkg) {
id = topology_physical_package_id(cpu);
target = -1;
if (has_cstate_pkg &&
cpumask_test_and_clear_cpu(cpu, &cstate_pkg_cpu_mask)) {
for_each_online_cpu(i) {
if (i == cpu)
continue;
if (id == topology_physical_package_id(i)) {
target = i;
break;
}
}
if (cpumask_test_and_clear_cpu(cpu, &cstate_pkg_cpu_mask) && target >= 0)
target = cpumask_any_but(topology_core_cpumask(cpu), cpu);
/* Migrate events if there is a valid target */
if (target < nr_cpu_ids) {
cpumask_set_cpu(target, &cstate_pkg_cpu_mask);
WARN_ON(cpumask_empty(&cstate_pkg_cpu_mask));
if (target >= 0)
perf_pmu_migrate_context(&cstate_pkg_pmu, cpu, target);
}
}
}
static void cstate_cpu_init(int cpu)
{
int i, id;
unsigned int target;
/* cpu init for cstate core */
if (has_cstate_core) {
id = topology_core_id(cpu);
for_each_cpu(i, &cstate_core_cpu_mask) {
if (id == topology_core_id(i))
break;
}
if (i >= nr_cpu_ids)
cpumask_set_cpu(cpu, &cstate_core_cpu_mask);
}
/*
* If this is the first online thread of that core, set it in
* the core cpu mask as the designated reader.
*/
target = cpumask_any_and(&cstate_core_cpu_mask,
topology_sibling_cpumask(cpu));
/* cpu init for cstate pkg */
if (has_cstate_pkg) {
id = topology_physical_package_id(cpu);
for_each_cpu(i, &cstate_pkg_cpu_mask) {
if (id == topology_physical_package_id(i))
break;
}
if (i >= nr_cpu_ids)
cpumask_set_cpu(cpu, &cstate_pkg_cpu_mask);
}
if (has_cstate_core && target >= nr_cpu_ids)
cpumask_set_cpu(cpu, &cstate_core_cpu_mask);
/*
* If this is the first online thread of that package, set it
* in the package cpu mask as the designated reader.
*/
target = cpumask_any_and(&cstate_pkg_cpu_mask,
topology_core_cpumask(cpu));
if (has_cstate_pkg && target >= nr_cpu_ids)
cpumask_set_cpu(cpu, &cstate_pkg_cpu_mask);
}
static int cstate_cpu_notifier(struct notifier_block *self,
unsigned long action, void *hcpu)
unsigned long action, void *hcpu)
{
unsigned int cpu = (long)hcpu;
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_UP_PREPARE:
break;
case CPU_STARTING:
cstate_cpu_init(cpu);
break;
case CPU_UP_CANCELED:
case CPU_DYING:
break;
case CPU_ONLINE:
case CPU_DEAD:
break;
case CPU_DOWN_PREPARE:
cstate_cpu_exit(cpu);
break;
default:
break;
}
return NOTIFY_OK;
}