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

[Jin, Yao]

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@xxxxxxxxxxxxxxx>
> > > ---
> > >   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