Re: [PATCH/RFC v3] perf core: Allow setting up max frame stack depth via sysctl

From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	David Ahern <dsahern@gmail.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Ingo Molnar <mingo@kernel.org>,
	Adrian Hunter <adrian.hunter@intel.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Alexei Starovoitov <ast@kernel.org>,
	He Kuang <hekuang@huawei.com>, Jiri Olsa <jolsa@redhat.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Milian Wolff <milian.wolff@kdab.com>,
	Namhyung Kim <namhyung@kernel.org>,
	Stephane Eranian <eranian@google.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Vince Weaver <vincent.weaver@maine.edu>,
	Wang Nan <wangnan0@huawei.com>, Zefan Li <lizefan@huawei.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH/RFC v3] perf core: Allow setting up max frame stack depth via sysctl
Date: Tue, 26 Apr 2016 13:33:21 -0300	[thread overview]
Message-ID: <20160426163321.GI11033@kernel.org> (raw)
In-Reply-To: <CAE40pdeG-TrtBNS10XDQx2ynFqRAhbgENrU7g-_3Oqho047E0A@mail.gmail.com>

Em Mon, Apr 25, 2016 at 05:49:38PM -0700, Brendan Gregg escreveu:
> On Mon, Apr 25, 2016 at 5:47 PM, Arnaldo Carvalho de Melo
> <arnaldo.melo@gmail.com> wrote:
> > Em Mon, Apr 25, 2016 at 05:44:00PM -0700, Alexei Starovoitov escreveu:
> >> On Mon, Apr 25, 2016 at 09:29:28PM -0300, Arnaldo Carvalho de Melo wrote:
> >> >     Because we only allocate the callchain percpu data structures when there
> >> >     is a user, which allows for changing the max easily, its just a matter
> >> >     of having no callchain users at that point.
> >> >
> >> >     Reported-and-Tested-by: Brendan Gregg <brendan.d.gregg@gmail.com>
> >> >     Acked-by: Alexei Starovoitov <ast@kernel.org>
> >>
> >> yep :)
> >> hopefully Brendan can give it another spin.
> >
> > Agreed, and I'm calling it a day anyway, Brendan, please consider
> > retesting, thanks,

> Will do, thanks!

> Brendan

So, for completeness, further testing it to see how far it goes on a 8GB
machine I got:

[root@emilia ~]# echo 131100 > /proc/sys/kernel/perf_event_max_stack 
[root@emilia ~]# perf record -g ls
Error:
The sys_perf_event_open() syscall returned with 12 (Cannot allocate memory) for event (cycles).
/bin/dmesg may provide additional information.
No CONFIG_PERF_EVENTS=y kernel support configured?

[root@emilia ~]#

[root@emilia ~]# echo 131000 > /proc/sys/kernel/perf_event_max_stack 
[root@emilia ~]# perf record -g usleep
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.013 MB perf.data (9 samples) ]
[root@emilia ~]# ls -la perf.data
-rw-------. 1 root root 15736 Apr 26 13:33 perf.data
[root@emilia ~]# 

- Arnaldo