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

Like Xu
2020-08-13T06:57:16Z

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
>
> 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
>>>>
>>>
>>