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SubjectRe: [PATCH v5 5/5] perf-stat: introduce bpf_counter_ops->disable()
On Mon, Apr 26, 2021 at 10:18:57PM +0000, Song Liu wrote:
>
>
> > On Apr 26, 2021, at 2:27 PM, Jiri Olsa <jolsa@redhat.com> wrote:
> >
> > On Sun, Apr 25, 2021 at 02:43:33PM -0700, Song Liu wrote:
> >
> > SNIP
> >
> >> +static inline int bpf_counter__disable(struct evsel *evsel __maybe_unused)
> >> +{
> >> + return 0;
> >> +}
> >> +
> >> static inline int bpf_counter__read(struct evsel *evsel __maybe_unused)
> >> {
> >> return -EAGAIN;
> >> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> >> index d29a8a118973c..e71041c890102 100644
> >> --- a/tools/perf/util/evlist.c
> >> +++ b/tools/perf/util/evlist.c
> >> @@ -17,6 +17,7 @@
> >> #include "evsel.h"
> >> #include "debug.h"
> >> #include "units.h"
> >> +#include "bpf_counter.h"
> >> #include <internal/lib.h> // page_size
> >> #include "affinity.h"
> >> #include "../perf.h"
> >> @@ -421,6 +422,9 @@ static void __evlist__disable(struct evlist *evlist, char *evsel_name)
> >> if (affinity__setup(&affinity) < 0)
> >> return;
> >>
> >> + evlist__for_each_entry(evlist, pos)
> >> + bpf_counter__disable(pos);
> >
> > I was wondering why you don't check evsel__is_bpf like
> > for the enable case.. and realized that we don't skip
> > bpf evsels in __evlist__enable and __evlist__disable
> > like we do in read_affinity_counters
> >
> > so I guess there's extra affinity setup and bunch of
> > wrong ioctls being called?
>
> We actually didn't do wrong ioctls because the following check:
>
> if (... || !pos->core.fd)
> continue;
>
> in __evlist__enable and __evlist__disable. That we don't allocate
> core.fd for is_bpf events.
>
> It is probably good to be more safe with an extra check of
> evsel__is_bpf(). But it is not required with current code.

hum, but it will do all the affinity setup no? for no reason,
if there's no non-bpb event

jirka

>
> Thanks,
> Song
>
> [...]
>

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