Re: [PATCH v5 5/5] perf-stat: introduce bpf_counter_ops->disable()
From: Song Liu
Date: Mon Apr 26 2021 - 18:19:07 EST
> On Apr 26, 2021, at 2:27 PM, Jiri Olsa <jolsa@xxxxxxxxxx> 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.
Thanks,
Song
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