[patch] perf_event_open.2 PERF_EVENT_IOC_PERIOD update

[patch] perf_event_open.2 PERF_EVENT_IOC_PERIOD update

[Vince Weaver]

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
--
To unsubscribe from this list: send the line "unsubscribe linux-man" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [patch] perf_event_open.2 PERF_EVENT_IOC_PERIOD update

[Michael Kerrisk (man-pages)]

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:
--
To unsubscribe from this list: send the line "unsubscribe linux-man" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html