linux-kernel - Re: [PATCH RFC V8 3/4] perf,tools: per-event callgraph support

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Date:	Wed, 5 Aug 2015 09:21:59 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Kan Liang <kan.liang@...el.com>
Cc:	acme@...nel.org, jolsa@...nel.org, namhyung@...nel.org,
	ak@...ux.intel.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC V8 3/4] perf,tools: per-event callgraph support

On Tue, Aug 04, 2015 at 04:30:21AM -0400, Kan Liang wrote:

SNIP

> +
> +	/* User explicitly set per-event callgraph, clear the old setting and reset. */
> +	if ((callgraph_buf != NULL) || (dump_size > 0)) {
> +
> +		/* parse callgraph parameters */
> +		if (callgraph_buf != NULL) {
> +			if (!strcmp(callgraph_buf, "no")) {
> +				param.enabled = false;
> +				param.record_mode = CALLCHAIN_NONE;
> +			} else {
> +				param.enabled = true;
> +				if (parse_callchain_record_opt(callgraph_buf, &param)) {
> +					pr_err("per-event callgraph setting for %s failed. "
> +					       "Apply callgraph global setting for it\n",
> +					       evsel->name);
> +					return;
> +				}
> +			}
> +		}
> +		if (dump_size > 0)
> +			param.dump_size = dump_size;

the parse_callchain_record_opt does some rounding on the stack size value
via the get_stack_size function, so following command like does not fail:

  $ perf record --call-graph='dwarf,819' ls

while the term syntax fails:
  $ perf record -e 'cpu/cpu-cycles,call-graph=dwarf,stack-size=819/

  Error:
  The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (cpu/cpu-cycles,time=0,call-graph=dwarf,stack-size=819/).
  /bin/dmesg may provide additional information.
  No CONFIG_PERF_EVENTS=y kernel support configured?


jirka
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