linux-kernel - Re: [PATCH 1/4] perf tools: Remove event types framework only user

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Date:	Thu, 11 Jul 2013 15:16:45 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	linux-kernel@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>, Paul Mackerras <paulus@...ba.org>,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	David Ahern <dsahern@...il.com>,
	Thomas Renninger <trenn@...e.de>
Subject: Re: [PATCH 1/4] perf tools: Remove event types framework only user

Hi Jiri,

On Tue,  9 Jul 2013 18:48:56 +0200, Jiri Olsa wrote:
> The only user of the event types data is 'perf timechart'
> command and uses this info to identify proper tracepoints
> based on its name.
>
> Switching this code to use traceevent library API to obtain
> IDs for needed tracepoints. This should also make the samples
> processing faster as we no longer compare strings but numbers.

A better way I think is using tracepoint handlers.  You don't need to
compare anything this way since an evsel can know its handler.

Please see perf_session__set_tracepoints_handlers() and builtin-
{kmem,lock,sched}.c.


[SNIP]
>  
> -/*
> - * trace_flag_type is an enumeration that holds different
> - * states when a trace occurs. These are:
> - *  IRQS_OFF            - interrupts were disabled
> - *  IRQS_NOSUPPORT      - arch does not support irqs_disabled_flags
> - *  NEED_RESCED         - reschedule is requested
> - *  HARDIRQ             - inside an interrupt handler
> - *  SOFTIRQ             - inside a softirq handler
> - */
> -enum trace_flag_type {
> -	TRACE_FLAG_IRQS_OFF		= 0x01,
> -	TRACE_FLAG_IRQS_NOSUPPORT	= 0x02,
> -	TRACE_FLAG_NEED_RESCHED		= 0x04,
> -	TRACE_FLAG_HARDIRQ		= 0x08,
> -	TRACE_FLAG_SOFTIRQ		= 0x10,
> -};

Why did you remove this part?  Isn't it used by elsewhere?  Anyway, it
seems unrelated to this change.


[SNIP]
> +static int get_id(const char *sys, const char *name, u32 *id)
> +{
> +	struct event_format *format;
> +
> +	format = event_format__new(sys, name);

No.  You need to access to tracepoints in the perf session data, not
ones in the current system.  The perf_session__set_tracepoints_handlers()
deals with it correctly.

Thanks,
Namhyung


> +	if (!format)
> +		return -1;
> +
> +	*id = format->id;
> +	pevent_free_format(format);
> +	return 0;
> +}
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