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

Jin, Yao
2020-08-13T07:08:31Z

On 8/13/2020 2:57 PM, Like Xu wrote:
> Hi Yao,
>
> On 2020/8/13 11:11, Jin, Yao wrote:
>> 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.
>
> It's true for the non ":u" case.
>
>>
>> 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.
>
> The patch changes the "perf kvm" original behavior.
>
> Testcase: perf kvm --host --guest --guestkallsyms=guest-kallsyms \
> --guestmodules=guest-modules record -e cycles:u ...
>
> From:
>
> 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
> dummy:HG: type: 1, size: 120, config: 0x9, { sample_period, sample_freq }: 4000, sample_type:
> IP|TID|TIME|ID|CPU|PERIOD, read_format: ID, inherit: 1, mmap: 1, comm: 1, freq: 1, task: 1,
> sample_id_all: 1, mmap2: 1, comm_exec: 1, ksymbol: 1, bpf_event: 1
>
> To:
>
> 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
>
> dummy:HG: type: 1, size: 120, config: 0x9, { sample_period, sample_freq }: 4000, sample_type:
> IP|TID|TIME|ID|CPU|PERIOD, read_format: ID, inherit: 1, mmap: 1, comm: 1, freq: 1, task: 1,
> sample_id_all: 1, mmap2: 1, comm_exec: 1, ksymbol: 1, bpf_event: 1
>
> Thanks,
> Like Xu

The behavior is similar as native kernel. The change of exclude_guest (0 -> 1) is expected.

On native kernel,

Before:

perf record -e cycles:u ./div
perf evlist -v
cycles:u: ..., exclude_kernel: 1, exclude_hv: 1, ...

After:

perf record -e cycles:u ./div
perf evlist -v
cycles:u: ..., exclude_kernel: 1, exclude_hv: 1, exclude_guest: 1, ...

Thanks
Jin Yao

>>
>> 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
>>>>>
>>>>
>>>
>