On 10/31/13, 11:23 AM, Harald Servat wrote:
Which is the relation between perf_clock() (or local_clock()) and
clock_gettime (CLOCK_MONOTONIC, ). Are they the same? If not, is there a
way to correlate them? Or alternatively, is it possible to call
local_clock() from the userland?
We still do not have a means of correlating perf_clock to time-of-day,
monotonic or any other clock source. Still trying.
Pawell Moll has a couple of patches posted -- one uses an ioctl to get
perf_clock timestamps the other makes perf_clock accessible through
clock_gettime. See attached.
David
>From 5e2d4c81b9e4a82090ec44a24e84223e00a4c5fd Mon Sep 17 00:00:00 2001
From: David Ahern <dsah...@gmail.com>
Date: Wed, 23 Oct 2013 16:53:05 +0100
Subject: [PATCH] perf: POSIX CLOCK_PERF to report current time value
To co-relate user space events with the perf events stream
a current (as in: "what time(stamp) is it now?") time value
must be made available.
This patch adds a POSIX clock returning the perf_clock()
value and accesible from userspace:
#include <time.h>
struct timespec ts;
clock_gettime(CLOCK_PERF, &ts);
Signed-off-by: Pawel Moll <pawel.m...@arm.com>
Signed-off-by: David Ahern <dsah...@gmail.com>
---
include/uapi/linux/time.h | 1 +
kernel/events/core.c | 20 ++++++++++++++++++++
2 files changed, 21 insertions(+)
diff --git a/include/uapi/linux/time.h b/include/uapi/linux/time.h
index e75e1b6ff27f..9066bf02c867 100644
--- a/include/uapi/linux/time.h
+++ b/include/uapi/linux/time.h
@@ -56,6 +56,7 @@ struct itimerval {
#define CLOCK_BOOTTIME_ALARM 9
#define CLOCK_SGI_CYCLE 10 /* Hardware specific */
#define CLOCK_TAI 11
+#define CLOCK_PERF 12
#define MAX_CLOCKS 16
#define CLOCKS_MASK (CLOCK_REALTIME | CLOCK_MONOTONIC)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index b073975af05a..98c26fb1d9fd 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -39,6 +39,7 @@
#include <linux/hw_breakpoint.h>
#include <linux/mm_types.h>
#include <linux/cgroup.h>
+#include <linux/posix-timers.h>
#include "internal.h"
@@ -303,6 +304,19 @@ static inline u64 perf_clock(void)
}
#endif
+static int perf_posix_clock_getres(const clockid_t which_clock,
+ struct timespec *tp)
+{
+ *tp = ns_to_timespec(TICK_NSEC);
+ return 0;
+}
+
+static int perf_posix_clock_get(clockid_t which_clock, struct timespec *tp)
+{
+ *tp = ns_to_timespec(perf_clock());
+ return 0;
+}
+
static inline struct perf_cpu_context *
__get_cpu_context(struct perf_event_context *ctx)
{
@@ -7878,6 +7892,10 @@ perf_cpu_notify(struct notifier_block *self, unsigned
long action, void *hcpu)
void __init perf_event_init(void)
{
+ struct k_clock perf_posix_clock = {
+ .clock_getres = perf_posix_clock_getres,
+ .clock_get = perf_posix_clock_get,
+ };
int ret;
idr_init(&pmu_idr);
@@ -7894,6 +7912,8 @@ void __init perf_event_init(void)
ret = init_hw_breakpoint();
WARN(ret, "hw_breakpoint initialization failed with: %d", ret);
+ posix_timers_register_clock(CLOCK_PERF, &perf_posix_clock);
+
/* do not patch jump label more than once per second */
jump_label_rate_limit(&perf_sched_events, HZ);
--
1.8.3.4 (Apple Git-47)
>From 3601ad205e74a0af22de4421f12a5f0ee0559057 Mon Sep 17 00:00:00 2001
From: Pawel Moll <pawel.m...@arm.com>
Date: Fri, 1 Feb 2013 14:03:56 +0000
Subject: [PATCH 16/45] perf: Add ioctl to return current time value
To co-relate user space events with the perf events stream
a current (as in: "what time(stamp) is it now?") time value
must be made available.
This patch adds a perf ioctl that makes this possible.
Signed-off-by: Pawel Moll <pawel.m...@arm.com>
---
include/uapi/linux/perf_event.h | 1 +
kernel/events/core.c | 8 ++++++++
2 files changed, 9 insertions(+)
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 0b1df41..41cb39e 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -321,6 +321,7 @@ struct perf_event_attr {
#define PERF_EVENT_IOC_PERIOD _IOW('$', 4, __u64)
#define PERF_EVENT_IOC_SET_OUTPUT _IO ('$', 5)
#define PERF_EVENT_IOC_SET_FILTER _IOW('$', 6, char *)
+#define PERF_EVENT_IOC_GET_TIME _IOR('$', 7, __u64)
enum perf_event_ioc_flags {
PERF_IOC_FLAG_GROUP = 1U << 0,
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 1833bc5..62a44d9 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3543,6 +3543,14 @@ static long perf_ioctl(struct file *file, unsigned int
cmd, unsigned long arg)
case PERF_EVENT_IOC_SET_FILTER:
return perf_event_set_filter(event, (void __user *)arg);
+ case PERF_EVENT_IOC_GET_TIME:
+ {
+ u64 time = perf_clock();
+ if (copy_to_user((void __user *)arg, &time, sizeof(time)))
+ return -EFAULT;
+ return 0;
+ }
+
default:
return -ENOTTY;
}
--
1.7.10.1
