linux-kernel - Re: [PATCH] perf tools: fix guest mode monitoring on AMD

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Date:	Mon, 27 Feb 2012 10:47:25 -0700
From:	David Ahern <dsahern@...il.com>
To:	Stephane Eranian <eranian@...gle.com>
CC:	linux-kernel@...r.kernel.org, acme@...hat.com,
	robert.richter@....com, peterz@...radead.org, mingo@...e.hu,
	joro@...tes.org, gleb@...hat.com
Subject: Re: [PATCH] perf tools: fix guest mode monitoring on AMD

On 2/27/12 10:33 AM, Stephane Eranian wrote:
> Commit:
>
> 1aed267 perf kvm: Do guest-only counting by default
>
> introduced a bug on AMD systems whereby simple commands:
>
> $ perf stat ls
> Performance counter stats for 'ls':
>                   0 cycles                    #    0.000 GHz
>         0.003704596 seconds time elapsed
>
> would not count anything anymore. Same results for perf record.
>
> I tracked it down to guest mode exclusion being enabled
> by default leading to attr->exclude_guest = 1. When
> not operating under any sort of virtualization, this
> causes the PMU not to count anything.
>
> The fix disables guest exclusion by default.
>
> Signed-off-by: Stephane Eranian<eranian@...gle.com>
> ---
>
> diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
> index 8109a90..c1017b3 100644
> --- a/tools/perf/util/util.c
> +++ b/tools/perf/util/util.c
> @@ -6,7 +6,7 @@
>    * XXX We need to find a better place for these things...
>    */
>   bool perf_host  = true;
> -bool perf_guest = false;
> +bool perf_guest = true;

This was recently reverted to false by 
c4a7dca92bbb9881a5d678720f1d0c2153499749

See: https://lkml.org/lkml/2012/2/8/234

David

>
>   void event_attr_init(struct perf_event_attr *attr)
>   {
> --
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