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Subject[PATCH 15/16] perf, persistent: Exposing persistent events using sysfs
Date
From: Robert Richter <robert.richter@calxeda.com>

Expose persistent events in the system to userland using sysfs. Perf
tools are able to read existing pmu events from sysfs. Now we use a
persistent pmu as an event container containing all registered
persistent events of the system. This patch adds dynamically
registration of persistent events to sysfs. E.g. something like this:

/sys/bus/event_source/devices/persistent/events/mce_record:persistent,config=106
/sys/bus/event_source/devices/persistent/format/persistent:attr5:23

Perf tools need to support the attr<num> syntax that is added in a
separate patch set. With it we are able to run perf tool commands to
read persistent events, e.g.:

# perf record -e persistent/mce_record/ sleep 10
# perf top -e persistent/mce_record/

Signed-off-by: Robert Richter <robert.richter@calxeda.com>
---
kernel/events/persistent.c | 55 +++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 54 insertions(+), 1 deletion(-)

diff --git a/kernel/events/persistent.c b/kernel/events/persistent.c
index d5093a3..a764144 100644
--- a/kernel/events/persistent.c
+++ b/kernel/events/persistent.c
@@ -17,8 +17,10 @@ struct pers_event_desc {
struct pers_event {
char *name;
struct perf_event_attr attr;
+ struct perf_pmu_events_attr sysfs;
};

+static struct pmu persistent_pmu;
static DEFINE_PER_CPU(struct list_head, pers_events);
static DEFINE_PER_CPU(struct mutex, pers_events_lock);

@@ -137,6 +139,8 @@ unwind:
return PTR_ERR(event);
}

+static int pers_event_sysfs_register(struct pers_event *event);
+
int perf_add_persistent_event_by_id(char* name, int id)
{
struct pers_event *event;
@@ -150,6 +154,8 @@ int perf_add_persistent_event_by_id(char* name, int id)
if (!event->name)
goto fail;

+ event->sysfs.id = id;
+
attr = &event->attr;
attr->sample_period = 1;
attr->wakeup_events = 1;
@@ -163,6 +169,8 @@ int perf_add_persistent_event_by_id(char* name, int id)
if (ret)
goto fail;

+ pers_event_sysfs_register(event);
+
return 0;
fail:
kfree(event->name);
@@ -204,12 +212,57 @@ static struct attribute_group persistent_format_group = {
.attrs = persistent_format_attrs,
};

+#define MAX_EVENTS 16
+
+static struct attribute *persistent_events_attr[MAX_EVENTS + 1] = { };
+
+static struct attribute_group persistent_events_group = {
+ .name = "events",
+ .attrs = persistent_events_attr,
+};
+
static const struct attribute_group *persistent_attr_groups[] = {
&persistent_format_group,
+ NULL, /* placeholder: &persistent_events_group */
NULL,
};
+#define EVENTS_GROUP (persistent_attr_groups[1])

-static struct pmu persistent_pmu;
+static ssize_t pers_event_sysfs_show(struct device *dev,
+ struct device_attribute *__attr, char *page)
+{
+ struct perf_pmu_events_attr *attr =
+ container_of(__attr, struct perf_pmu_events_attr, attr);
+ return sprintf(page, "persistent,config=%lld",
+ (unsigned long long)attr->id);
+}
+
+static int pers_event_sysfs_register(struct pers_event *event)
+{
+ struct device_attribute *attr = &event->sysfs.attr;
+ int idx;
+
+ *attr = (struct device_attribute)__ATTR(, 0444, pers_event_sysfs_show,
+ NULL);
+ attr->attr.name = event->name;
+
+ /* add sysfs attr to events: */
+ for (idx = 0; idx < MAX_EVENTS; idx++) {
+ if (!cmpxchg(persistent_events_attr + idx, NULL, &attr->attr))
+ break;
+ }
+
+ if (idx >= MAX_EVENTS)
+ return -ENOSPC;
+ if (!idx)
+ EVENTS_GROUP = &persistent_events_group;
+ if (!persistent_pmu.dev)
+ return 0; /* sysfs not yet initialized */
+ if (idx)
+ return sysfs_update_group(&persistent_pmu.dev->kobj,
+ EVENTS_GROUP);
+ return sysfs_create_group(&persistent_pmu.dev->kobj, EVENTS_GROUP);
+}

static int persistent_pmu_init(struct perf_event *event)
{
--
1.8.1.1


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