Re: [PATCH] perf parse-events: Set exclude_guest for user-space counting

Jin, Yao
2020-08-13T03:11:52Z

Hi Like,

On 8/12/2020 9:02 PM, Like Xu wrote:
> On 2020/8/12 20:15, Arnaldo Carvalho de Melo wrote:
>> Em Wed, Aug 12, 2020 at 02:59:53PM +0800, Jin Yao escreveu:
>>> Currently if we run 'perf record -e cycles:u', exclude_guest is 0.
>>>
>>> But it doesn't make sense that we request for user-space counting
>>> but we also get the guest report.
>>>
>
> Please hold the horse and allow this possibility.
>
> Some authorized perf users on the host may
> only want to count (KVM) guest user space events.
>
> Thanks,
> Like Xu
>

Without this patch, if we don't set the ":u" modifier, exclude_guest = 1.

perf record -e cycles ./div
perf evlist -v
cycles: size: 120, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|PERIOD,
read_format: ID, disabled: 1, inherit: 1, mmap: 1, comm: 1, freq: 1, enable_on_exec: 1, task: 1,
sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1, ksymbol: 1, bpf_event: 1

So this patch doesn't change perf's original behavior.

Thanks
Jin Yao

>>> To keep perf semantics consistent and clear, this patch sets
>>> exclude_guest for user-space counting.
>>
>> Applied, and also added this, that you should consider doing in the
>> future (modulo the "Committer testing:" header :) ):
>>
>> Committer testing:
>>
>> Before:
>>
>>    # perf record -e cycles:u
>>    ^C[ perf record: Woken up 1 times to write data ]
>>    [ perf record: Captured and wrote 1.231 MB perf.data (91 samples) ]
>>    #
>>    # perf evlist -v
>>    cycles:u: size: 120, { sample_period, sample_freq }: 4000, sample_type:
>> IP|TID|TIME|ID|CPU|PERIOD, read_format: ID, disabled: 1, inherit: 1, exclude_kernel: 1,
>> exclude_hv: 1, freq: 1, sample_id_all: 1
>>    <SNIP>
>>    #
>>
>> After:
>>
>>    # perf record -e cycles:u
>>    ^C[ perf record: Woken up 1 times to write data ]
>>    [ perf record: Captured and wrote 1.263 MB perf.data (403 samples) ]
>>    #
>>    # perf evlist -v
>>    cycles:u: size: 120, { sample_period, sample_freq }: 4000, sample_type:
>> IP|TID|TIME|ID|CPU|PERIOD, read_format: ID, disabled: 1, inherit: 1, exclude_kernel: 1,
>> exclude_hv: 1, freq: 1, sample_id_all: 1, exclude_guest: 1
>>    #
>>
>> ----
>>
>> I.e. show actual command output before and after that demonstrates the
>> problem and then the solution.
>>
>>> Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
>>> ---
>>>   tools/perf/util/parse-events.c | 2 ++
>>>   1 file changed, 2 insertions(+)
>>>
>>> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
>>> index 9f7260e69113..4d809f1fe269 100644
>>> --- a/tools/perf/util/parse-events.c
>>> +++ b/tools/perf/util/parse-events.c
>>> @@ -1794,6 +1794,8 @@ static int get_event_modifier(struct event_modifier *mod, char *str,
>>>           if (*str == 'u') {
>>>               if (!exclude)
>>>                   exclude = eu = ek = eh = 1;
>>> +            if (!exclude_GH)
>>> +                eG = 1;
>>>               eu = 0;
>>>           } else if (*str == 'k') {
>>>               if (!exclude)
>>> --
>>> 2.17.1
>>>
>>
>