linux-kernel - Re: [PATCH v5 5/5] perf-stat: introduce bpf_counter

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Message-ID: <YJAV4vBUFr6sz5tM@kernel.org>
Date:   Mon, 3 May 2021 12:25:22 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Song Liu <songliubraving@...com>, Song Liu <song@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Kernel Team <Kernel-team@...com>,
        "acme@...hat.com" <acme@...hat.com>,
        "namhyung@...nel.org" <namhyung@...nel.org>,
        "jolsa@...nel.org" <jolsa@...nel.org>
Subject: Re: [PATCH v5 5/5] perf-stat: introduce bpf_counter_ops->disable()

Em Mon, May 03, 2021 at 04:09:45PM +0200, Jiri Olsa escreveu:
> On Thu, Apr 29, 2021 at 10:40:01PM +0000, Song Liu wrote:
> 
> SNIP
> 
> > >>>>> #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

> > > Yes, it will do the affinity setup. Let me see how to get something
> > > like all_counters_use_bpf here (or within builtin-stat.c).

> > Would something like the following work? It is not clean (skipping some 
> > useful logic in __evlist__[enable|disable]). But it seems to work in the
> > tests.

> sorry for late reply, but I can't no longer apply this:
 
> 	patching file tools/perf/builtin-stat.c
> 	Hunk #1 FAILED at 572.
> 	Hunk #2 FAILED at 581.
> 	2 out of 2 hunks FAILED -- saving rejects to file tools/perf/builtin-stat.c.rej
> 	patching file tools/perf/util/evlist.c
> 	Hunk #1 FAILED at 425.
> 	1 out of 1 hunk FAILED -- saving rejects to file tools/perf/util/evlist.c.rej
 
> ah, I see the patchset got already merged.. not sure why I'm doing review then ;-)

Hey, sometimes this can happen, sorry. Song, please submit on top of
what is upstream.

- Arnaldo