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

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Date:	Tue, 26 Apr 2016 13:33:21 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Brendan Gregg <brendan.d.gregg@...il.com>
Cc:	Alexei Starovoitov <alexei.starovoitov@...il.com>,
	David Ahern <dsahern@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Alexei Starovoitov <ast@...nel.org>,
	He Kuang <hekuang@...wei.com>, Jiri Olsa <jolsa@...hat.com>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Milian Wolff <milian.wolff@...b.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Stephane Eranian <eranian@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Vince Weaver <vincent.weaver@...ne.edu>,
	Wang Nan <wangnan0@...wei.com>, Zefan Li <lizefan@...wei.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH/RFC v3] perf core: Allow setting up max frame stack depth
 via sysctl

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@...il.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@...il.com>
> >> >     Acked-by: Alexei Starovoitov <ast@...nel.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@...lia ~]# echo 131100 > /proc/sys/kernel/perf_event_max_stack 
[root@...lia ~]# 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@...lia ~]#

[root@...lia ~]# echo 131000 > /proc/sys/kernel/perf_event_max_stack 
[root@...lia ~]# 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@...lia ~]# ls -la perf.data
-rw-------. 1 root root 15736 Apr 26 13:33 perf.data
[root@...lia ~]# 

- Arnaldo