Re: [PATCH 4/5] perf tools: Allow to ignore missing pid

[Arnaldo Carvalho de Melo]

Em Mon, Dec 12, 2016 at 03:53:12PM +0100, Jiri Olsa escreveu:
> On Mon, Dec 12, 2016 at 11:32:09AM -0300, Arnaldo Carvalho de Melo wrote:
> > Em Mon, Dec 12, 2016 at 11:35:42AM +0100, Jiri Olsa escreveu:
> > > Adding perf_evsel::ignore_missing_cpu_thread bool.
> > > 
> > > When set true, it allows perf to ignore error of missing
> > > pid of perf event syscall.
> > > 
> > > We remove missing thread id from the thread_map, so the
> > > rest of the processing like ioctl and mmap won't get
> > > disturbed with -1 fd
> > 
> > What was the test performed? I tried it here the following while doing
> > a 'make -j4 allmodconfig' in the background, i.e. tons of threads coming
> > and going, and I sometimes get:
> > 
> > [root@jouet ~]# perf record -u acme 
> > Error:
> > The sys_perf_event_open() syscall returned with 3 (No such process) for
> > event (cycles:ppp).
> > /bin/dmesg may provide additional information.
> > No CONFIG_PERF_EVENTS=y kernel support configured?
> 
> I dont think it's fast enough (start/stop) to hit the race, I've got best
> results with having on background this:
> 
>   while :; do /usr/bin/true; done

Ok, but the focus of my message wasn't on generating threads, was in
having the above happen with your patch applied.

- Arnaldo