This change allows events to use PERF_SAMPLE READ with inherit
so long as PERF_SAMPLE_TID is also set.
In this configuration, an event will be inherited into any
child processes / threads, allowing convenient profiling of a
multiprocess or multithreaded application, whilst allowing
profiling tools to collect per-thread samples, in particular
of groups of counters.
The read_format field of both PERF_RECORD_READ and PERF_RECORD_SAMPLE
are changed by this new configuration, but calls to `read()` on the same
event file descriptor are unaffected and continue to return the
cumulative total.
Signed-off-by: Ben Gainey <[email protected]>
---
include/linux/perf_event.h | 1 +
kernel/events/core.c | 82 ++++++++++++++++++++++++++++----------
2 files changed, 62 insertions(+), 21 deletions(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index d2a15c0c6f8a..e7eed33c50f1 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -932,6 +932,7 @@ struct perf_event_context {
int nr_task_data;
int nr_stat;
+ int nr_inherit_read;
int nr_freq;
int rotate_disable;
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 724e6d7e128f..bf0639a2e2b1 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1767,6 +1767,18 @@ perf_event_groups_next(struct perf_event *event, struct pmu *pmu)
event = rb_entry_safe(rb_next(&event->group_node), \
typeof(*event), group_node))
+/*
+ * Does the event attribute request inherit with PERF_SAMPLE_READ
+ */
+#define perf_attr_has_inherit_and_sample_read(attr) \
+ ((attr)->inherit && ((attr)->sample_type & PERF_SAMPLE_READ))
+
+/*
+ * Does the event request an attribte that requests inherit with PERF_SAMPLE_READ
+ */
+#define perf_event_has_inherit_and_sample_read(event) \
+ perf_attr_has_inherit_and_sample_read(&((event)->attr))
+
/*
* Add an event from the lists for its context.
* Must be called with ctx->mutex and ctx->lock held.
@@ -1797,6 +1809,8 @@ list_add_event(struct perf_event *event, struct perf_event_context *ctx)
ctx->nr_user++;
if (event->attr.inherit_stat)
ctx->nr_stat++;
+ if (perf_event_has_inherit_and_sample_read(event))
+ ctx->nr_inherit_read++;
if (event->state > PERF_EVENT_STATE_OFF)
perf_cgroup_event_enable(event, ctx);
@@ -2021,6 +2035,8 @@ list_del_event(struct perf_event *event, struct perf_event_context *ctx)
ctx->nr_user--;
if (event->attr.inherit_stat)
ctx->nr_stat--;
+ if (perf_event_has_inherit_and_sample_read(event))
+ ctx->nr_inherit_read--;
list_del_rcu(&event->event_entry);
@@ -3529,11 +3545,18 @@ perf_event_context_sched_out(struct task_struct *task, struct task_struct *next)
perf_ctx_disable(ctx, false);
/* PMIs are disabled; ctx->nr_pending is stable. */
- if (local_read(&ctx->nr_pending) ||
+ if (ctx->nr_inherit_read ||
+ next_ctx->nr_inherit_read ||
+ local_read(&ctx->nr_pending) ||
local_read(&next_ctx->nr_pending)) {
/*
* Must not swap out ctx when there's pending
* events that rely on the ctx->task relation.
+ *
+ * Likewise, when a context contains inherit +
+ * SAMPLE_READ events they should be switched
+ * out using the slow path so that they are
+ * treated as if they were distinct contexts.
*/
raw_spin_unlock(&next_ctx->lock);
rcu_read_unlock();
@@ -4533,11 +4556,19 @@ static void __perf_event_read(void *info)
raw_spin_unlock(&ctx->lock);
}
-static inline u64 perf_event_count(struct perf_event *event)
+static inline u64 perf_event_count_cumulative(struct perf_event *event)
{
return local64_read(&event->count) + atomic64_read(&event->child_count);
}
+static inline u64 perf_event_count(struct perf_event *event, bool self_value_only)
+{
+ if (self_value_only && perf_event_has_inherit_and_sample_read(event))
+ return local64_read(&event->count);
+
+ return perf_event_count_cumulative(event);
+}
+
static void calc_timer_values(struct perf_event *event,
u64 *now,
u64 *enabled,
@@ -5454,7 +5485,7 @@ static u64 __perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *
mutex_lock(&event->child_mutex);
(void)perf_event_read(event, false);
- total += perf_event_count(event);
+ total += perf_event_count_cumulative(event);
*enabled += event->total_time_enabled +
atomic64_read(&event->child_total_time_enabled);
@@ -5463,7 +5494,7 @@ static u64 __perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *
list_for_each_entry(child, &event->child_list, child_list) {
(void)perf_event_read(child, false);
- total += perf_event_count(child);
+ total += perf_event_count_cumulative(child);
*enabled += child->total_time_enabled;
*running += child->total_time_running;
}
@@ -5545,14 +5576,14 @@ static int __perf_read_group_add(struct perf_event *leader,
/*
* Write {count,id} tuples for every sibling.
*/
- values[n++] += perf_event_count(leader);
+ values[n++] += perf_event_count_cumulative(leader);
if (read_format & PERF_FORMAT_ID)
values[n++] = primary_event_id(leader);
if (read_format & PERF_FORMAT_LOST)
values[n++] = atomic64_read(&leader->lost_samples);
for_each_sibling_event(sub, leader) {
- values[n++] += perf_event_count(sub);
+ values[n++] += perf_event_count_cumulative(sub);
if (read_format & PERF_FORMAT_ID)
values[n++] = primary_event_id(sub);
if (read_format & PERF_FORMAT_LOST)
@@ -6132,7 +6163,7 @@ void perf_event_update_userpage(struct perf_event *event)
++userpg->lock;
barrier();
userpg->index = perf_event_index(event);
- userpg->offset = perf_event_count(event);
+ userpg->offset = perf_event_count_cumulative(event);
if (userpg->index)
userpg->offset -= local64_read(&event->hw.prev_count);
@@ -7194,13 +7225,14 @@ void perf_event__output_id_sample(struct perf_event *event,
static void perf_output_read_one(struct perf_output_handle *handle,
struct perf_event *event,
- u64 enabled, u64 running)
+ u64 enabled, u64 running,
+ bool from_sample)
{
u64 read_format = event->attr.read_format;
u64 values[5];
int n = 0;
- values[n++] = perf_event_count(event);
+ values[n++] = perf_event_count(event, from_sample);
if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED) {
values[n++] = enabled +
atomic64_read(&event->child_total_time_enabled);
@@ -7218,8 +7250,9 @@ static void perf_output_read_one(struct perf_output_handle *handle,
}
static void perf_output_read_group(struct perf_output_handle *handle,
- struct perf_event *event,
- u64 enabled, u64 running)
+ struct perf_event *event,
+ u64 enabled, u64 running,
+ bool from_sample)
{
struct perf_event *leader = event->group_leader, *sub;
u64 read_format = event->attr.read_format;
@@ -7245,7 +7278,7 @@ static void perf_output_read_group(struct perf_output_handle *handle,
(leader->state == PERF_EVENT_STATE_ACTIVE))
leader->pmu->read(leader);
- values[n++] = perf_event_count(leader);
+ values[n++] = perf_event_count(leader, from_sample);
if (read_format & PERF_FORMAT_ID)
values[n++] = primary_event_id(leader);
if (read_format & PERF_FORMAT_LOST)
@@ -7260,7 +7293,7 @@ static void perf_output_read_group(struct perf_output_handle *handle,
(sub->state == PERF_EVENT_STATE_ACTIVE))
sub->pmu->read(sub);
- values[n++] = perf_event_count(sub);
+ values[n++] = perf_event_count(sub, from_sample);
if (read_format & PERF_FORMAT_ID)
values[n++] = primary_event_id(sub);
if (read_format & PERF_FORMAT_LOST)
@@ -7281,9 +7314,14 @@ static void perf_output_read_group(struct perf_output_handle *handle,
* The problem is that its both hard and excessively expensive to iterate the
* child list, not to mention that its impossible to IPI the children running
* on another CPU, from interrupt/NMI context.
+ *
+ * Instead the combination of PERF_SAMPLE_READ and inherit will track per-thread
+ * counts rather than attempting to accumulate some value across all children on
+ * all cores.
*/
static void perf_output_read(struct perf_output_handle *handle,
- struct perf_event *event)
+ struct perf_event *event,
+ bool from_sample)
{
u64 enabled = 0, running = 0, now;
u64 read_format = event->attr.read_format;
@@ -7301,9 +7339,9 @@ static void perf_output_read(struct perf_output_handle *handle,
calc_timer_values(event, &now, &enabled, &running);
if (event->attr.read_format & PERF_FORMAT_GROUP)
- perf_output_read_group(handle, event, enabled, running);
+ perf_output_read_group(handle, event, enabled, running, from_sample);
else
- perf_output_read_one(handle, event, enabled, running);
+ perf_output_read_one(handle, event, enabled, running, from_sample);
}
void perf_output_sample(struct perf_output_handle *handle,
@@ -7343,7 +7381,7 @@ void perf_output_sample(struct perf_output_handle *handle,
perf_output_put(handle, data->period);
if (sample_type & PERF_SAMPLE_READ)
- perf_output_read(handle, event);
+ perf_output_read(handle, event, true);
if (sample_type & PERF_SAMPLE_CALLCHAIN) {
int size = 1;
@@ -7944,7 +7982,7 @@ perf_event_read_event(struct perf_event *event,
return;
perf_output_put(&handle, read_event);
- perf_output_read(&handle, event);
+ perf_output_read(&handle, event, false);
perf_event__output_id_sample(event, &handle, &sample);
perf_output_end(&handle);
@@ -12006,10 +12044,12 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
local64_set(&hwc->period_left, hwc->sample_period);
/*
- * We currently do not support PERF_SAMPLE_READ on inherited events.
+ * We do not support PERF_SAMPLE_READ on inherited events unless
+ * PERF_SAMPLE_TID is also selected, which allows inherited events to
+ * collect per-thread samples.
* See perf_output_read().
*/
- if (attr->inherit && (attr->sample_type & PERF_SAMPLE_READ))
+ if (perf_attr_has_inherit_and_sample_read(attr) && !(attr->sample_type & PERF_SAMPLE_TID))
goto err_ns;
if (!has_branch_stack(event))
@@ -13033,7 +13073,7 @@ static void sync_child_event(struct perf_event *child_event)
perf_event_read_event(child_event, task);
}
- child_val = perf_event_count(child_event);
+ child_val = perf_event_count_cumulative(child_event);
/*
* Add back the child's count to the parent's count:
--
2.44.0
Hello,
On Mon, Apr 15, 2024 at 1:15 AM Ben Gainey <[email protected]> wrote:
>
> This change allows events to use PERF_SAMPLE READ with inherit
> so long as PERF_SAMPLE_TID is also set.
>
> In this configuration, an event will be inherited into any
> child processes / threads, allowing convenient profiling of a
> multiprocess or multithreaded application, whilst allowing
> profiling tools to collect per-thread samples, in particular
> of groups of counters.
>
> The read_format field of both PERF_RECORD_READ and PERF_RECORD_SAMPLE
> are changed by this new configuration, but calls to `read()` on the same
> event file descriptor are unaffected and continue to return the
> cumulative total.
>
> Signed-off-by: Ben Gainey <[email protected]>
Looks ok to me now, some nitpicks below.
> ---
> include/linux/perf_event.h | 1 +
> kernel/events/core.c | 82 ++++++++++++++++++++++++++++----------
> 2 files changed, 62 insertions(+), 21 deletions(-)
>
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index d2a15c0c6f8a..e7eed33c50f1 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -932,6 +932,7 @@ struct perf_event_context {
>
> int nr_task_data;
> int nr_stat;
> + int nr_inherit_read;
> int nr_freq;
> int rotate_disable;
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 724e6d7e128f..bf0639a2e2b1 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -1767,6 +1767,18 @@ perf_event_groups_next(struct perf_event *event, struct pmu *pmu)
> event = rb_entry_safe(rb_next(&event->group_node), \
> typeof(*event), group_node))
>
> +/*
> + * Does the event attribute request inherit with PERF_SAMPLE_READ
> + */
> +#define perf_attr_has_inherit_and_sample_read(attr) \
Looks somewhat verbose. Can it be just
has_inherit_sample_read() ? Also you can make it static inline.
> + ((attr)->inherit && ((attr)->sample_type & PERF_SAMPLE_READ))
> +
> +/*
> + * Does the event request an attribte that requests inherit with PERF_SAMPLE_READ
typo: attribte
> + */
> +#define perf_event_has_inherit_and_sample_read(event) \
> + perf_attr_has_inherit_and_sample_read(&((event)->attr))
> +
> /*
> * Add an event from the lists for its context.
> * Must be called with ctx->mutex and ctx->lock held.
> @@ -1797,6 +1809,8 @@ list_add_event(struct perf_event *event, struct perf_event_context *ctx)
> ctx->nr_user++;
> if (event->attr.inherit_stat)
> ctx->nr_stat++;
> + if (perf_event_has_inherit_and_sample_read(event))
> + ctx->nr_inherit_read++;
>
> if (event->state > PERF_EVENT_STATE_OFF)
> perf_cgroup_event_enable(event, ctx);
> @@ -2021,6 +2035,8 @@ list_del_event(struct perf_event *event, struct perf_event_context *ctx)
> ctx->nr_user--;
> if (event->attr.inherit_stat)
> ctx->nr_stat--;
> + if (perf_event_has_inherit_and_sample_read(event))
> + ctx->nr_inherit_read--;
>
> list_del_rcu(&event->event_entry);
>
> @@ -3529,11 +3545,18 @@ perf_event_context_sched_out(struct task_struct *task, struct task_struct *next)
> perf_ctx_disable(ctx, false);
>
> /* PMIs are disabled; ctx->nr_pending is stable. */
> - if (local_read(&ctx->nr_pending) ||
> + if (ctx->nr_inherit_read ||
> + next_ctx->nr_inherit_read ||
> + local_read(&ctx->nr_pending) ||
> local_read(&next_ctx->nr_pending)) {
> /*
> * Must not swap out ctx when there's pending
> * events that rely on the ctx->task relation.
> + *
> + * Likewise, when a context contains inherit +
> + * SAMPLE_READ events they should be switched
> + * out using the slow path so that they are
> + * treated as if they were distinct contexts.
> */
> raw_spin_unlock(&next_ctx->lock);
> rcu_read_unlock();
> @@ -4533,11 +4556,19 @@ static void __perf_event_read(void *info)
> raw_spin_unlock(&ctx->lock);
> }
>
> -static inline u64 perf_event_count(struct perf_event *event)
> +static inline u64 perf_event_count_cumulative(struct perf_event *event)
> {
> return local64_read(&event->count) + atomic64_read(&event->child_count);
> }
Maybe it's better to leave it as is and add a new wrapper below.
At least it'd create a smaller diff. :)
>
> +static inline u64 perf_event_count(struct perf_event *event, bool self_value_only)
> +{
> + if (self_value_only && perf_event_has_inherit_and_sample_read(event))
> + return local64_read(&event->count);
> +
> + return perf_event_count_cumulative(event);
> +}
> +
> static void calc_timer_values(struct perf_event *event,
> u64 *now,
> u64 *enabled,
> @@ -5454,7 +5485,7 @@ static u64 __perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *
> mutex_lock(&event->child_mutex);
>
> (void)perf_event_read(event, false);
> - total += perf_event_count(event);
> + total += perf_event_count_cumulative(event);
>
> *enabled += event->total_time_enabled +
> atomic64_read(&event->child_total_time_enabled);
> @@ -5463,7 +5494,7 @@ static u64 __perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *
>
> list_for_each_entry(child, &event->child_list, child_list) {
> (void)perf_event_read(child, false);
> - total += perf_event_count(child);
> + total += perf_event_count_cumulative(child);
> *enabled += child->total_time_enabled;
> *running += child->total_time_running;
> }
> @@ -5545,14 +5576,14 @@ static int __perf_read_group_add(struct perf_event *leader,
> /*
> * Write {count,id} tuples for every sibling.
> */
> - values[n++] += perf_event_count(leader);
> + values[n++] += perf_event_count_cumulative(leader);
> if (read_format & PERF_FORMAT_ID)
> values[n++] = primary_event_id(leader);
> if (read_format & PERF_FORMAT_LOST)
> values[n++] = atomic64_read(&leader->lost_samples);
>
> for_each_sibling_event(sub, leader) {
> - values[n++] += perf_event_count(sub);
> + values[n++] += perf_event_count_cumulative(sub);
> if (read_format & PERF_FORMAT_ID)
> values[n++] = primary_event_id(sub);
> if (read_format & PERF_FORMAT_LOST)
> @@ -6132,7 +6163,7 @@ void perf_event_update_userpage(struct perf_event *event)
> ++userpg->lock;
> barrier();
> userpg->index = perf_event_index(event);
> - userpg->offset = perf_event_count(event);
> + userpg->offset = perf_event_count_cumulative(event);
> if (userpg->index)
> userpg->offset -= local64_read(&event->hw.prev_count);
>
> @@ -7194,13 +7225,14 @@ void perf_event__output_id_sample(struct perf_event *event,
>
> static void perf_output_read_one(struct perf_output_handle *handle,
> struct perf_event *event,
> - u64 enabled, u64 running)
> + u64 enabled, u64 running,
> + bool from_sample)
> {
> u64 read_format = event->attr.read_format;
> u64 values[5];
> int n = 0;
>
> - values[n++] = perf_event_count(event);
> + values[n++] = perf_event_count(event, from_sample);
> if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED) {
> values[n++] = enabled +
> atomic64_read(&event->child_total_time_enabled);
> @@ -7218,8 +7250,9 @@ static void perf_output_read_one(struct perf_output_handle *handle,
> }
>
> static void perf_output_read_group(struct perf_output_handle *handle,
> - struct perf_event *event,
> - u64 enabled, u64 running)
> + struct perf_event *event,
> + u64 enabled, u64 running,
> + bool from_sample)
> {
> struct perf_event *leader = event->group_leader, *sub;
> u64 read_format = event->attr.read_format;
> @@ -7245,7 +7278,7 @@ static void perf_output_read_group(struct perf_output_handle *handle,
> (leader->state == PERF_EVENT_STATE_ACTIVE))
> leader->pmu->read(leader);
>
> - values[n++] = perf_event_count(leader);
> + values[n++] = perf_event_count(leader, from_sample);
> if (read_format & PERF_FORMAT_ID)
> values[n++] = primary_event_id(leader);
> if (read_format & PERF_FORMAT_LOST)
> @@ -7260,7 +7293,7 @@ static void perf_output_read_group(struct perf_output_handle *handle,
> (sub->state == PERF_EVENT_STATE_ACTIVE))
> sub->pmu->read(sub);
>
> - values[n++] = perf_event_count(sub);
> + values[n++] = perf_event_count(sub, from_sample);
> if (read_format & PERF_FORMAT_ID)
> values[n++] = primary_event_id(sub);
> if (read_format & PERF_FORMAT_LOST)
> @@ -7281,9 +7314,14 @@ static void perf_output_read_group(struct perf_output_handle *handle,
> * The problem is that its both hard and excessively expensive to iterate the
> * child list, not to mention that its impossible to IPI the children running
> * on another CPU, from interrupt/NMI context.
> + *
> + * Instead the combination of PERF_SAMPLE_READ and inherit will track per-thread
> + * counts rather than attempting to accumulate some value across all children on
> + * all cores.
> */
> static void perf_output_read(struct perf_output_handle *handle,
> - struct perf_event *event)
> + struct perf_event *event,
> + bool from_sample)
> {
> u64 enabled = 0, running = 0, now;
> u64 read_format = event->attr.read_format;
> @@ -7301,9 +7339,9 @@ static void perf_output_read(struct perf_output_handle *handle,
> calc_timer_values(event, &now, &enabled, &running);
>
> if (event->attr.read_format & PERF_FORMAT_GROUP)
> - perf_output_read_group(handle, event, enabled, running);
> + perf_output_read_group(handle, event, enabled, running, from_sample);
> else
> - perf_output_read_one(handle, event, enabled, running);
> + perf_output_read_one(handle, event, enabled, running, from_sample);
> }
>
> void perf_output_sample(struct perf_output_handle *handle,
> @@ -7343,7 +7381,7 @@ void perf_output_sample(struct perf_output_handle *handle,
> perf_output_put(handle, data->period);
>
> if (sample_type & PERF_SAMPLE_READ)
> - perf_output_read(handle, event);
> + perf_output_read(handle, event, true);
>
> if (sample_type & PERF_SAMPLE_CALLCHAIN) {
> int size = 1;
> @@ -7944,7 +7982,7 @@ perf_event_read_event(struct perf_event *event,
> return;
>
> perf_output_put(&handle, read_event);
> - perf_output_read(&handle, event);
> + perf_output_read(&handle, event, false);
> perf_event__output_id_sample(event, &handle, &sample);
>
> perf_output_end(&handle);
> @@ -12006,10 +12044,12 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
> local64_set(&hwc->period_left, hwc->sample_period);
>
> /*
> - * We currently do not support PERF_SAMPLE_READ on inherited events.
> + * We do not support PERF_SAMPLE_READ on inherited events unless
> + * PERF_SAMPLE_TID is also selected, which allows inherited events to
> + * collect per-thread samples.
> * See perf_output_read().
> */
> - if (attr->inherit && (attr->sample_type & PERF_SAMPLE_READ))
> + if (perf_attr_has_inherit_and_sample_read(attr) && !(attr->sample_type & PERF_SAMPLE_TID))
If you leave the original condition and just add a check
for _TID, you can get rid of the perf_attr_ function.
Thanks,
Namhyung
> goto err_ns;
>
> if (!has_branch_stack(event))
> @@ -13033,7 +13073,7 @@ static void sync_child_event(struct perf_event *child_event)
> perf_event_read_event(child_event, task);
> }
>
> - child_val = perf_event_count(child_event);
> + child_val = perf_event_count_cumulative(child_event);
>
> /*
> * Add back the child's count to the parent's count:
> --
> 2.44.0
>
On Thu, 2024-05-09 at 16:40 -0700, Namhyung Kim wrote:
> Hello,
>
> On Mon, Apr 15, 2024 at 1:15 AM Ben Gainey <[email protected]>
> wrote:
> >
> > This change allows events to use PERF_SAMPLE READ with inherit
> > so long as PERF_SAMPLE_TID is also set.
> >
> > In this configuration, an event will be inherited into any
> > child processes / threads, allowing convenient profiling of a
> > multiprocess or multithreaded application, whilst allowing
> > profiling tools to collect per-thread samples, in particular
> > of groups of counters.
> >
> > The read_format field of both PERF_RECORD_READ and
> > PERF_RECORD_SAMPLE
> > are changed by this new configuration, but calls to `read()` on the
> > same
> > event file descriptor are unaffected and continue to return the
> > cumulative total.
> >
> > Signed-off-by: Ben Gainey <[email protected]>
>
> Looks ok to me now, some nitpicks below.
>
Thanks. I've a couple of replies below, otherwise I'll sort this out
and rebase onto v6.9 unless there is a better tag/branch to target?
Ben
>
> > ---
> > include/linux/perf_event.h | 1 +
> > kernel/events/core.c | 82 ++++++++++++++++++++++++++++------
> > ----
> > 2 files changed, 62 insertions(+), 21 deletions(-)
> >
> > diff --git a/include/linux/perf_event.h
> > b/include/linux/perf_event.h
> > index d2a15c0c6f8a..e7eed33c50f1 100644
> > --- a/include/linux/perf_event.h
> > +++ b/include/linux/perf_event.h
> > @@ -932,6 +932,7 @@ struct perf_event_context {
> >
> > int nr_task_data;
> > int nr_stat;
> > + int nr_inherit_read;
> > int nr_freq;
> > int rotate_disable;
> >
> > diff --git a/kernel/events/core.c b/kernel/events/core.c
> > index 724e6d7e128f..bf0639a2e2b1 100644
> > --- a/kernel/events/core.c
> > +++ b/kernel/events/core.c
> > @@ -1767,6 +1767,18 @@ perf_event_groups_next(struct perf_event
> > *event, struct pmu *pmu)
> > event = rb_entry_safe(rb_next(&event-
> > >group_node), \
> > typeof(*event), group_node))
> >
> > +/*
> > + * Does the event attribute request inherit with PERF_SAMPLE_READ
> > + */
> > +#define
> > perf_attr_has_inherit_and_sample_read(attr) \
>
> Looks somewhat verbose. Can it be just
> has_inherit_sample_read() ? Also you can make it static inline.
>
>
> > + ((attr)->inherit && ((attr)->sample_type &
> > PERF_SAMPLE_READ))
> > +
> > +/*
> > + * Does the event request an attribte that requests inherit with
> > PERF_SAMPLE_READ
>
> typo: attribte
>
>
> > + */
> > +#define
> > perf_event_has_inherit_and_sample_read(event) \
> > + perf_attr_has_inherit_and_sample_read(&((event)->attr))
> > +
> > /*
> > * Add an event from the lists for its context.
> > * Must be called with ctx->mutex and ctx->lock held.
> > @@ -1797,6 +1809,8 @@ list_add_event(struct perf_event *event,
> > struct perf_event_context *ctx)
> > ctx->nr_user++;
> > if (event->attr.inherit_stat)
> > ctx->nr_stat++;
> > + if (perf_event_has_inherit_and_sample_read(event))
> > + ctx->nr_inherit_read++;
> >
> > if (event->state > PERF_EVENT_STATE_OFF)
> > perf_cgroup_event_enable(event, ctx);
> > @@ -2021,6 +2035,8 @@ list_del_event(struct perf_event *event,
> > struct perf_event_context *ctx)
> > ctx->nr_user--;
> > if (event->attr.inherit_stat)
> > ctx->nr_stat--;
> > + if (perf_event_has_inherit_and_sample_read(event))
> > + ctx->nr_inherit_read--;
> >
> > list_del_rcu(&event->event_entry);
> >
> > @@ -3529,11 +3545,18 @@ perf_event_context_sched_out(struct
> > task_struct *task, struct task_struct *next)
> > perf_ctx_disable(ctx, false);
> >
> > /* PMIs are disabled; ctx->nr_pending is
> > stable. */
> > - if (local_read(&ctx->nr_pending) ||
> > + if (ctx->nr_inherit_read ||
> > + next_ctx->nr_inherit_read ||
> > + local_read(&ctx->nr_pending) ||
> > local_read(&next_ctx->nr_pending)) {
> > /*
> > * Must not swap out ctx when
> > there's pending
> > * events that rely on the ctx-
> > >task relation.
> > + *
> > + * Likewise, when a context
> > contains inherit +
> > + * SAMPLE_READ events they should
> > be switched
> > + * out using the slow path so that
> > they are
> > + * treated as if they were distinct
> > contexts.
> > */
> > raw_spin_unlock(&next_ctx->lock);
> > rcu_read_unlock();
> > @@ -4533,11 +4556,19 @@ static void __perf_event_read(void *info)
> > raw_spin_unlock(&ctx->lock);
> > }
> >
> > -static inline u64 perf_event_count(struct perf_event *event)
> > +static inline u64 perf_event_count_cumulative(struct perf_event
> > *event)
> > {
> > return local64_read(&event->count) + atomic64_read(&event-
> > >child_count);
> > }
>
> Maybe it's better to leave it as is and add a new wrapper below.
> At least it'd create a smaller diff. :)
I can do that, but the reason I did it this way was to avoid some
future easy-to-make-mistake because someone picks up the
`perf_event_count(struct perf_event*)` when they should have used
something else. With this change any future refactor / work requires
some developer to pick between `perf_event_count_cumulative` and
`perf_event_count(..., bool self_value_only)` which feels marginally
less error prone since. Please let me know if you'd still like this one
changed.
>
> >
> > +static inline u64 perf_event_count(struct perf_event *event, bool
> > self_value_only)
> > +{
> > + if (self_value_only &&
> > perf_event_has_inherit_and_sample_read(event))
> > + return local64_read(&event->count);
> > +
> > + return perf_event_count_cumulative(event);
> > +}
> > +
> > static void calc_timer_values(struct perf_event *event,
> > u64 *now,
> > u64 *enabled,
> > @@ -5454,7 +5485,7 @@ static u64 __perf_event_read_value(struct
> > perf_event *event, u64 *enabled, u64 *
> > mutex_lock(&event->child_mutex);
> >
> > (void)perf_event_read(event, false);
> > - total += perf_event_count(event);
> > + total += perf_event_count_cumulative(event);
> >
> > *enabled += event->total_time_enabled +
> > atomic64_read(&event-
> > >child_total_time_enabled);
> > @@ -5463,7 +5494,7 @@ static u64 __perf_event_read_value(struct
> > perf_event *event, u64 *enabled, u64 *
> >
> > list_for_each_entry(child, &event->child_list, child_list)
> > {
> > (void)perf_event_read(child, false);
> > - total += perf_event_count(child);
> > + total += perf_event_count_cumulative(child);
> > *enabled += child->total_time_enabled;
> > *running += child->total_time_running;
> > }
> > @@ -5545,14 +5576,14 @@ static int __perf_read_group_add(struct
> > perf_event *leader,
> > /*
> > * Write {count,id} tuples for every sibling.
> > */
> > - values[n++] += perf_event_count(leader);
> > + values[n++] += perf_event_count_cumulative(leader);
> > if (read_format & PERF_FORMAT_ID)
> > values[n++] = primary_event_id(leader);
> > if (read_format & PERF_FORMAT_LOST)
> > values[n++] = atomic64_read(&leader->lost_samples);
> >
> > for_each_sibling_event(sub, leader) {
> > - values[n++] += perf_event_count(sub);
> > + values[n++] += perf_event_count_cumulative(sub);
> > if (read_format & PERF_FORMAT_ID)
> > values[n++] = primary_event_id(sub);
> > if (read_format & PERF_FORMAT_LOST)
> > @@ -6132,7 +6163,7 @@ void perf_event_update_userpage(struct
> > perf_event *event)
> > ++userpg->lock;
> > barrier();
> > userpg->index = perf_event_index(event);
> > - userpg->offset = perf_event_count(event);
> > + userpg->offset = perf_event_count_cumulative(event);
> > if (userpg->index)
> > userpg->offset -= local64_read(&event-
> > >hw.prev_count);
> >
> > @@ -7194,13 +7225,14 @@ void perf_event__output_id_sample(struct
> > perf_event *event,
> >
> > static void perf_output_read_one(struct perf_output_handle
> > *handle,
> > struct perf_event *event,
> > - u64 enabled, u64 running)
> > + u64 enabled, u64 running,
> > + bool from_sample)
> > {
> > u64 read_format = event->attr.read_format;
> > u64 values[5];
> > int n = 0;
> >
> > - values[n++] = perf_event_count(event);
> > + values[n++] = perf_event_count(event, from_sample);
> > if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED) {
> > values[n++] = enabled +
> > atomic64_read(&event-
> > >child_total_time_enabled);
> > @@ -7218,8 +7250,9 @@ static void perf_output_read_one(struct
> > perf_output_handle *handle,
> > }
> >
> > static void perf_output_read_group(struct perf_output_handle
> > *handle,
> > - struct perf_event *event,
> > - u64 enabled, u64 running)
> > + struct perf_event *event,
> > + u64 enabled, u64 running,
> > + bool from_sample)
> > {
> > struct perf_event *leader = event->group_leader, *sub;
> > u64 read_format = event->attr.read_format;
> > @@ -7245,7 +7278,7 @@ static void perf_output_read_group(struct
> > perf_output_handle *handle,
> > (leader->state == PERF_EVENT_STATE_ACTIVE))
> > leader->pmu->read(leader);
> >
> > - values[n++] = perf_event_count(leader);
> > + values[n++] = perf_event_count(leader, from_sample);
> > if (read_format & PERF_FORMAT_ID)
> > values[n++] = primary_event_id(leader);
> > if (read_format & PERF_FORMAT_LOST)
> > @@ -7260,7 +7293,7 @@ static void perf_output_read_group(struct
> > perf_output_handle *handle,
> > (sub->state == PERF_EVENT_STATE_ACTIVE))
> > sub->pmu->read(sub);
> >
> > - values[n++] = perf_event_count(sub);
> > + values[n++] = perf_event_count(sub, from_sample);
> > if (read_format & PERF_FORMAT_ID)
> > values[n++] = primary_event_id(sub);
> > if (read_format & PERF_FORMAT_LOST)
> > @@ -7281,9 +7314,14 @@ static void perf_output_read_group(struct
> > perf_output_handle *handle,
> > * The problem is that its both hard and excessively expensive to
> > iterate the
> > * child list, not to mention that its impossible to IPI the
> > children running
> > * on another CPU, from interrupt/NMI context.
> > + *
> > + * Instead the combination of PERF_SAMPLE_READ and inherit will
> > track per-thread
> > + * counts rather than attempting to accumulate some value across
> > all children on
> > + * all cores.
> > */
> > static void perf_output_read(struct perf_output_handle *handle,
> > - struct perf_event *event)
> > + struct perf_event *event,
> > + bool from_sample)
> > {
> > u64 enabled = 0, running = 0, now;
> > u64 read_format = event->attr.read_format;
> > @@ -7301,9 +7339,9 @@ static void perf_output_read(struct
> > perf_output_handle *handle,
> > calc_timer_values(event, &now, &enabled, &running);
> >
> > if (event->attr.read_format & PERF_FORMAT_GROUP)
> > - perf_output_read_group(handle, event, enabled,
> > running);
> > + perf_output_read_group(handle, event, enabled,
> > running, from_sample);
> > else
> > - perf_output_read_one(handle, event, enabled,
> > running);
> > + perf_output_read_one(handle, event, enabled,
> > running, from_sample);
> > }
> >
> > void perf_output_sample(struct perf_output_handle *handle,
> > @@ -7343,7 +7381,7 @@ void perf_output_sample(struct
> > perf_output_handle *handle,
> > perf_output_put(handle, data->period);
> >
> > if (sample_type & PERF_SAMPLE_READ)
> > - perf_output_read(handle, event);
> > + perf_output_read(handle, event, true);
> >
> > if (sample_type & PERF_SAMPLE_CALLCHAIN) {
> > int size = 1;
> > @@ -7944,7 +7982,7 @@ perf_event_read_event(struct perf_event
> > *event,
> > return;
> >
> > perf_output_put(&handle, read_event);
> > - perf_output_read(&handle, event);
> > + perf_output_read(&handle, event, false);
> > perf_event__output_id_sample(event, &handle, &sample);
> >
> > perf_output_end(&handle);
> > @@ -12006,10 +12044,12 @@ perf_event_alloc(struct perf_event_attr
> > *attr, int cpu,
> > local64_set(&hwc->period_left, hwc->sample_period);
> >
> > /*
> > - * We currently do not support PERF_SAMPLE_READ on
> > inherited events.
> > + * We do not support PERF_SAMPLE_READ on inherited events
> > unless
> > + * PERF_SAMPLE_TID is also selected, which allows inherited
> > events to
> > + * collect per-thread samples.
> > * See perf_output_read().
> > */
> > - if (attr->inherit && (attr->sample_type &
> > PERF_SAMPLE_READ))
> > + if (perf_attr_has_inherit_and_sample_read(attr) && !(attr-
> > >sample_type & PERF_SAMPLE_TID))
>
> If you leave the original condition and just add a check
> for _TID, you can get rid of the perf_attr_ function.
True, though `perf_event_has_inherit_and_sample_read` is defined in
terms of `perf_attr_has_inherit_and_sample_read`, and whilst this is
the only other use of `perf_attr_has_inherit_and_sample_read`, it the
_event_ version is used in several places, so this mostly just keeps
the two consistent. Please let me know if you'd still like this one
changed.
>
> Thanks,
> Namhyung
>
>
> > goto err_ns;
> >
> > if (!has_branch_stack(event))
> > @@ -13033,7 +13073,7 @@ static void sync_child_event(struct
> > perf_event *child_event)
> > perf_event_read_event(child_event, task);
> > }
> >
> > - child_val = perf_event_count(child_event);
> > + child_val = perf_event_count_cumulative(child_event);
> >
> > /*
> > * Add back the child's count to the parent's count:
> > --
> > 2.44.0
> >
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