Subject: Re: [PATCH v11 perf, bpf-next 7/9] perf tools: synthesize PERF_RECORD_* for loaded BPF programs

From: Jiri Olsa <[email-masked]>
Date: Tue, 22 Jan 2019 15:51:19 +0100

On Tue, Jan 22, 2019 at 12:31:17PM -0200, Arnaldo Carvalho de Melo wrote:
> Em Tue, Jan 22, 2019 at 12:13:20PM -0200, Arnaldo Carvalho de Melo escreveu:
> > Em Fri, Jan 18, 2019 at 11:46:55AM -0300, Arnaldo Carvalho de Melo escreveu:
> > > Em Thu, Jan 17, 2019 at 08:15:19AM -0800, Song Liu escreveu:
> > > > This patch synthesize PERF_RECORD_KSYMBOL and PERF_RECORD_BPF_EVENT for
> > > > BPF programs loaded before perf-record. This is achieved by gathering
> > > > information about all BPF programs via sys_bpf.
> > > 
> > > Ditto
> > 
> > This is breaking 'perf sched', see below, the fix seems trivial:
> > 
> > [root@quaco ~]# perf sched record -a sleep 2
> > [ perf record: Woken up 1 times to write data ]
> > 0x5b60 [0x138]: failed to process type: 17
> > [ perf record: Captured and wrote 1.539 MB perf.data ]
> > [root@quaco ~]# perf sched lat
> > 0x5b60 [0x138]: failed to process type: 17
> > Failed to process events, error -22
> > [root@quaco ~]#
> 
> So:
> 
>    perf_session__process_event (event->header.type = 17 (PERF_RECORD_KSYMBOL)
>      if (tool->ordered_events)
>        ret = perf_evlist__parse_sample_timestamp(evlist, event, &timestamp);
>        if (ret && ret != -1)
>             return ret;
> 
> So it returns here with -EFAULT, i.e. this is failing:
> 
> int perf_evlist__parse_sample_timestamp(struct perf_evlist *evlist,
>                                         union perf_event *event,
>                                         u64 *timestamp)
> {
>         struct perf_evsel *evsel = perf_evlist__event2evsel(evlist, event);
> 
>         if (!evsel)
>                 return -EFAULT;
>         return perf_evsel__parse_sample_timestamp(evsel, event, timestamp);
> }
> 
> It isn't mapping the event ID it finds back to an evsel.. Jiri, ideas?
> 
> This is happening so far only for 'perf sched', perf record with two
> events works.

I saw also perf mem failing because of this.. will check

jirka