* [patch] perf_event_open.2 PERF_EVENT_IOC_PERIOD update
@ 2013-10-28 13:33 Vince Weaver
[not found] ` <alpine.DEB.2.10.1310280927280.22634-6xBS8L8d439fDsnSvq7Uq4Se7xf15W0s1dQoKJhdanU@public.gmane.org>
0 siblings, 1 reply; 2+ messages in thread
From: Vince Weaver @ 2013-10-28 13:33 UTC (permalink / raw)
To: Michael Kerrisk (man-pages); +Cc: linux-man-u79uwXL29TY76Z2rM5mHXA
The PERF_EVENT_IOC_PERIOD ioctl was broken until 2.6.36, and it turns out
that the ARM architecture has some differing behavior too.
Reported-by: Andreas Sandberg <andreas.sandberg-1zs4UD6AkMk@public.gmane.org>
Signed-off-by: Vince Weaver <vincent.weaver-e7X0jjDqjFGHXe+LvDLADg@public.gmane.org>
diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2
index f4cb5bd..f337a27 100644
--- a/man2/perf_event_open.2
+++ b/man2/perf_event_open.2
@@ -1976,11 +1976,17 @@ reset, even if the event specified is not the group leader
(but see BUGS).
.TP
.B PERF_EVENT_IOC_PERIOD
-IOC_PERIOD is the command to update the period; it
-does not update the current period but instead defers until next.
+This updates the overflow period for the event.
+On most architectures the new period does not take effect until
+after the next overflow happens;
+on ARM since Linux 3.7 the period is updated immediately.
The argument is a pointer to a 64-bit value containing the
desired new period.
+
+Prior to Linux 2.6.36 this ioctl always failed due to a bug
+in the kernel.
+
.TP
.B PERF_EVENT_IOC_SET_OUTPUT
This tells the kernel to report event notifications to the specified
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^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [patch] perf_event_open.2 PERF_EVENT_IOC_PERIOD update
[not found] ` <alpine.DEB.2.10.1310280927280.22634-6xBS8L8d439fDsnSvq7Uq4Se7xf15W0s1dQoKJhdanU@public.gmane.org>
@ 2013-10-30 1:46 ` Michael Kerrisk (man-pages)
0 siblings, 0 replies; 2+ messages in thread
From: Michael Kerrisk (man-pages) @ 2013-10-30 1:46 UTC (permalink / raw)
To: Vince Weaver; +Cc: linux-man-u79uwXL29TY76Z2rM5mHXA
On 29.10.2013 02:33, Vince Weaver wrote:
>
> The PERF_EVENT_IOC_PERIOD ioctl was broken until 2.6.36, and it turns out
> that the ARM architecture has some differing behavior too.
Applied.
Thanks,
Michael
> Reported-by: Andreas Sandberg <andreas.sandberg-1zs4UD6AkMk@public.gmane.org>
> Signed-off-by: Vince Weaver <vincent.weaver-e7X0jjDqjFGHXe+LvDLADg@public.gmane.org>
>
> diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2
> index f4cb5bd..f337a27 100644
> --- a/man2/perf_event_open.2
> +++ b/man2/perf_event_open.2
> @@ -1976,11 +1976,17 @@ reset, even if the event specified is not the group leader
> (but see BUGS).
> .TP
> .B PERF_EVENT_IOC_PERIOD
> -IOC_PERIOD is the command to update the period; it
> -does not update the current period but instead defers until next.
> +This updates the overflow period for the event.
> +On most architectures the new period does not take effect until
> +after the next overflow happens;
> +on ARM since Linux 3.7 the period is updated immediately.
>
> The argument is a pointer to a 64-bit value containing the
> desired new period.
> +
> +Prior to Linux 2.6.36 this ioctl always failed due to a bug
> +in the kernel.
> +
> .TP
> .B PERF_EVENT_IOC_SET_OUTPUT
> This tells the kernel to report event notifications to the specified
>
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
My next Linux/UNIX system programming course:
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2013-10-28 13:33 [patch] perf_event_open.2 PERF_EVENT_IOC_PERIOD update Vince Weaver
[not found] ` <alpine.DEB.2.10.1310280927280.22634-6xBS8L8d439fDsnSvq7Uq4Se7xf15W0s1dQoKJhdanU@public.gmane.org>
2013-10-30 1:46 ` Michael Kerrisk (man-pages)
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