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authorPeter Zijlstra <peterz@infradead.org>2015-02-20 14:05:38 +0100
committerIngo Molnar <mingo@kernel.org>2015-03-27 10:13:22 +0100
commit34f439278cef7b1177f8ce24f9fc81dfc6221d3b (patch)
tree8bd86bf3d73aff36e8bee13c0102c7ae7e44e40c /kernel/events
parentb381e63b48a0b6befc7b4e55408c39012a0dcf8c (diff)
perf: Add per event clockid support
While thinking on the whole clock discussion it occurred to me we have two distinct uses of time: 1) the tracking of event/ctx/cgroup enabled/running/stopped times which includes the self-monitoring support in struct perf_event_mmap_page. 2) the actual timestamps visible in the data records. And we've been conflating them. The first is all about tracking time deltas, nobody should really care in what time base that happens, its all relative information, as long as its internally consistent it works. The second however is what people are worried about when having to merge their data with external sources. And here we have the discussion on MONOTONIC vs MONOTONIC_RAW etc.. Where MONOTONIC is good for correlating between machines (static offset), MONOTNIC_RAW is required for correlating against a fixed rate hardware clock. This means configurability; now 1) makes that hard because it needs to be internally consistent across groups of unrelated events; which is why we had to have a global perf_clock(). However, for 2) it doesn't really matter, perf itself doesn't care what it writes into the buffer. The below patch makes the distinction between these two cases by adding perf_event_clock() which is used for the second case. It further makes this configurable on a per-event basis, but adds a few sanity checks such that we cannot combine events with different clocks in confusing ways. And since we then have per-event configurability we might as well retain the 'legacy' behaviour as a default. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: David Ahern <dsahern@gmail.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: John Stultz <john.stultz@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/events')
-rw-r--r--kernel/events/core.c77
1 files changed, 74 insertions, 3 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index bb1a7c36e794..c40c2cac2d8e 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -327,6 +327,11 @@ static inline u64 perf_clock(void)
return local_clock();
}
+static inline u64 perf_event_clock(struct perf_event *event)
+{
+ return event->clock();
+}
+
static inline struct perf_cpu_context *
__get_cpu_context(struct perf_event_context *ctx)
{
@@ -4762,7 +4767,7 @@ static void __perf_event_header__init_id(struct perf_event_header *header,
}
if (sample_type & PERF_SAMPLE_TIME)
- data->time = perf_clock();
+ data->time = perf_event_clock(event);
if (sample_type & (PERF_SAMPLE_ID | PERF_SAMPLE_IDENTIFIER))
data->id = primary_event_id(event);
@@ -5340,6 +5345,8 @@ static void perf_event_task_output(struct perf_event *event,
task_event->event_id.tid = perf_event_tid(event, task);
task_event->event_id.ptid = perf_event_tid(event, current);
+ task_event->event_id.time = perf_event_clock(event);
+
perf_output_put(&handle, task_event->event_id);
perf_event__output_id_sample(event, &handle, &sample);
@@ -5373,7 +5380,7 @@ static void perf_event_task(struct task_struct *task,
/* .ppid */
/* .tid */
/* .ptid */
- .time = perf_clock(),
+ /* .time */
},
};
@@ -5749,7 +5756,7 @@ static void perf_log_throttle(struct perf_event *event, int enable)
.misc = 0,
.size = sizeof(throttle_event),
},
- .time = perf_clock(),
+ .time = perf_event_clock(event),
.id = primary_event_id(event),
.stream_id = event->id,
};
@@ -6293,6 +6300,8 @@ static int perf_swevent_init(struct perf_event *event)
static struct pmu perf_swevent = {
.task_ctx_nr = perf_sw_context,
+ .capabilities = PERF_PMU_CAP_NO_NMI,
+
.event_init = perf_swevent_init,
.add = perf_swevent_add,
.del = perf_swevent_del,
@@ -6636,6 +6645,8 @@ static int cpu_clock_event_init(struct perf_event *event)
static struct pmu perf_cpu_clock = {
.task_ctx_nr = perf_sw_context,
+ .capabilities = PERF_PMU_CAP_NO_NMI,
+
.event_init = cpu_clock_event_init,
.add = cpu_clock_event_add,
.del = cpu_clock_event_del,
@@ -6715,6 +6726,8 @@ static int task_clock_event_init(struct perf_event *event)
static struct pmu perf_task_clock = {
.task_ctx_nr = perf_sw_context,
+ .capabilities = PERF_PMU_CAP_NO_NMI,
+
.event_init = task_clock_event_init,
.add = task_clock_event_add,
.del = task_clock_event_del,
@@ -7200,6 +7213,10 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
event->hw.target = task;
}
+ event->clock = &local_clock;
+ if (parent_event)
+ event->clock = parent_event->clock;
+
if (!overflow_handler && parent_event) {
overflow_handler = parent_event->overflow_handler;
context = parent_event->overflow_handler_context;
@@ -7422,6 +7439,12 @@ perf_event_set_output(struct perf_event *event, struct perf_event *output_event)
if (output_event->cpu == -1 && output_event->ctx != event->ctx)
goto out;
+ /*
+ * Mixing clocks in the same buffer is trouble you don't need.
+ */
+ if (output_event->clock != event->clock)
+ goto out;
+
set:
mutex_lock(&event->mmap_mutex);
/* Can't redirect output if we've got an active mmap() */
@@ -7454,6 +7477,43 @@ static void mutex_lock_double(struct mutex *a, struct mutex *b)
mutex_lock_nested(b, SINGLE_DEPTH_NESTING);
}
+static int perf_event_set_clock(struct perf_event *event, clockid_t clk_id)
+{
+ bool nmi_safe = false;
+
+ switch (clk_id) {
+ case CLOCK_MONOTONIC:
+ event->clock = &ktime_get_mono_fast_ns;
+ nmi_safe = true;
+ break;
+
+ case CLOCK_MONOTONIC_RAW:
+ event->clock = &ktime_get_raw_fast_ns;
+ nmi_safe = true;
+ break;
+
+ case CLOCK_REALTIME:
+ event->clock = &ktime_get_real_ns;
+ break;
+
+ case CLOCK_BOOTTIME:
+ event->clock = &ktime_get_boot_ns;
+ break;
+
+ case CLOCK_TAI:
+ event->clock = &ktime_get_tai_ns;
+ break;
+
+ default:
+ return -EINVAL;
+ }
+
+ if (!nmi_safe && !(event->pmu->capabilities & PERF_PMU_CAP_NO_NMI))
+ return -EINVAL;
+
+ return 0;
+}
+
/**
* sys_perf_event_open - open a performance event, associate it to a task/cpu
*
@@ -7569,6 +7629,12 @@ SYSCALL_DEFINE5(perf_event_open,
*/
pmu = event->pmu;
+ if (attr.use_clockid) {
+ err = perf_event_set_clock(event, attr.clockid);
+ if (err)
+ goto err_alloc;
+ }
+
if (group_leader &&
(is_software_event(event) != is_software_event(group_leader))) {
if (is_software_event(event)) {
@@ -7618,6 +7684,11 @@ SYSCALL_DEFINE5(perf_event_open,
*/
if (group_leader->group_leader != group_leader)
goto err_context;
+
+ /* All events in a group should have the same clock */
+ if (group_leader->clock != event->clock)
+ goto err_context;
+
/*
* Do not allow to attach to a group in a different
* task or CPU context: