Re: [patch] perf_event_open.2: Exclude_hv clarification

["Michael Kerrisk (man-pages)" <mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Hi Paul Mackerass,

Would you be willing to review/comment on Vince's patch, please.

Cheers,

Michael

On 02/11/2015 08:04 PM, Vince Weaver wrote:
> 
> This manpage patch relates to the exclude_hv bit added to the kernel
> in the following commit:
> 
>     exclude_hv; Linux 2.6.31
>         commit 0475f9ea8e2cc030298908949e0d5da9f2fc2cfe
>         Author: Paul Mackerras <paulus-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>
> 
>             perf_counters: allow users to count user, kernel and/or hypervisor events
> 
>             Signed-off-by: Paul Mackerras <paulus-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>
> 
> The updated manpage text points out that the exclude_hv 
> "exclude hypervisor" bit only applies on hardware that 
> supports this  feature (such as PowerPC)
> and is silently ignored on other platforms such as x86.
> 
> This is a resend of the patch; the previous time I sent it
> (http://thread.gmane.org/gmane.linux.man/7500) it did not
> receive any comments.
> 
> 
> 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 39c8d8c..665aa31 100644
> --- a/man2/perf_event_open.2
> +++ b/man2/perf_event_open.2
> @@ -856,10 +856,9 @@ If this bit is set, the count excludes events that happen in kernel-space.
>  .IR "exclude_hv"
>  If this bit is set, the count excludes events that happen in the
>  hypervisor.
> -This is mainly for PMUs that have built-in support for handling this
> -(such as POWER).
> -Extra support is needed for handling hypervisor measurements on most
> -machines.
> +This is mainly for PMUs that have built-in hardware support
> +for this feature (such as POWER; this setting is silently
> +ignored on x86).
>  .TP
>  .IR "exclude_idle"
>  If set, don't count when the CPU is idle.
> 


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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