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Subject: Re: [PATCH v3] perf parse-events: Set exclude_guest=1 for user-space
 counting
To:     Arnaldo Carvalho de Melo <acme@kernel.org>
Cc:     jolsa@kernel.org, peterz@infradead.org, mingo@redhat.com,
        alexander.shishkin@linux.intel.com, Linux-kernel@vger.kernel.org,
        ak@linux.intel.com, kan.liang@intel.com, yao.jin@intel.com,
        like.xu@linux.intel.com
References: <20200814012120.16647-1-yao.jin@linux.intel.com>
 <20200814124722.GG13995@kernel.org>
From:   "Jin, Yao" <yao.jin@linux.intel.com>
Message-ID: <b061052d-592d-67d7-045f-481974b0687a@linux.intel.com>
Date:   Mon, 17 Aug 2020 10:32:49 +0800
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Hi Arnaldo,

On 8/14/2020 8:47 PM, Arnaldo Carvalho de Melo wrote:
> Em Fri, Aug 14, 2020 at 09:21:20AM +0800, Jin Yao escreveu:
>> Currently if we run 'perf record -e cycles:u', exclude_guest=0.
>>
>> But it doesn't make sense in most cases that we request for
>> user-space counting but we also get the guest report.
>>
>> Of course, we also need to consider perf kvm usage case that
>> authorized perf users on the host may only want to count guest
>> user space events. For example,
>>
>> perf kvm --guest record -e cycles:u
> Ok, probably this works, but what if I want to record guest user samples
> without using 'perf kvm'?
> 
> Can we have a 'U' modifier, perhaps, for that?
> 
> I.e.
> 
> perf record -e cycles:uU would not set exclude_host not exclude_guest,
> cycles:u excludes guest user, cycles:U excludes host user, would that be
> possible?
> 
> Anyway, I think that with what we have, your patch makes sense, having a
> way to, without using 'perf kvm' still be able to sample the guest can
> be done on top. of this.
> 
> Xu, can we get your Reviewed-by if this addresses your concerns?
> 
> - Arnaldo
>   

Do you suggest we will create a new modifier 'U' as a follow-up patch?

cycles:u - Count host user space but it doesn't count the guest user space (exclude_host = 0, 
exclude_guest = 1, exclude_kernel = 1, exclude_user = 0, exclude_hv = 1)

cycles:U - Count the guest user space but it doesn't count the host user space (exclude_host = 1, 
exclude_guest = 0, exclude_kernel = 1, exclude_user = 0, exclude_hv = 1)

Is above understanding correct?

Thanks
Jin Yao