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

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Message-ID: <YJAEKfvUXFPCik5+@krava>
Date:   Mon, 3 May 2021 16:09:45 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Song Liu <songliubraving@...com>
Cc:     Song Liu <song@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Kernel Team <Kernel-team@...com>,
        "acme@...nel.org" <acme@...nel.org>,
        "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()

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 ;-)

thanks,
jirka