linux-kernel - Re: [PATCH 3/5] perf probe: Support multiprobe event

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Message-ID: <20191106195630.GC11935@kernel.org>
Date:   Wed, 6 Nov 2019 16:56:30 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org,
        Tom Zanussi <tom.zanussi@...ux.intel.com>,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>,
        Namhyung Kim <namhyung@...nel.org>
Subject: Re: [PATCH 3/5] perf probe: Support multiprobe event

Em Tue, Nov 05, 2019 at 09:17:09AM +0900, Masami Hiramatsu escreveu:
> Support multiprobe event if the event is based on function
> and lines and kernel supports it. In this case, perf probe
> creates the first probe with an event, and tries to append
> following probes on that event, since those probes must be
> on the same source code line.
> 
> Before this patch;
>   # perf probe -a vfs_read:18
>   Added new events:
>     probe:vfs_read_L18   (on vfs_read:18)
>     probe:vfs_read_L18_1 (on vfs_read:18)

So this seems to depend on the previous one, I'll leave it for later,
till we figure that one out,

- Arnaldo
 
>   You can now use it in all perf tools, such as:
> 
>   	perf record -e probe:vfs_read_L18_1 -aR sleep 1
> 
>   #
> 
> After this patch (on multiprobe supported kernel)
>   # perf probe -a vfs_read:18
>   Added new events:
>     probe:vfs_read_L18   (on vfs_read:18)
>     probe:vfs_read_L18   (on vfs_read:18)
> 
>   You can now use it in all perf tools, such as:
> 
>   	perf record -e probe:vfs_read_L18 -aR sleep 1
> 
>   #
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> ---
>  tools/perf/util/probe-event.c |    9 +++++++--
>  tools/perf/util/probe-file.c  |    7 +++++++
>  tools/perf/util/probe-file.h  |    1 +
>  3 files changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> index d14b970a6461..23db6786c3ea 100644
> --- a/tools/perf/util/probe-event.c
> +++ b/tools/perf/util/probe-event.c
> @@ -2738,8 +2738,13 @@ static int probe_trace_event__set_name(struct probe_trace_event *tev,
>  	if (tev->event == NULL || tev->group == NULL)
>  		return -ENOMEM;
>  
> -	/* Add added event name to namelist */
> -	strlist__add(namelist, event);
> +	/*
> +	 * Add new event name to namelist if multiprobe event is NOT
> +	 * supported, since we have to use new event name for following
> +	 * probes in that case.
> +	 */
> +	if (!multiprobe_event_is_supported())
> +		strlist__add(namelist, event);
>  	return 0;
>  }
>  
> diff --git a/tools/perf/util/probe-file.c b/tools/perf/util/probe-file.c
> index b659466ea498..a63f1a19b0e8 100644
> --- a/tools/perf/util/probe-file.c
> +++ b/tools/perf/util/probe-file.c
> @@ -1007,6 +1007,7 @@ enum ftrace_readme {
>  	FTRACE_README_KRETPROBE_OFFSET,
>  	FTRACE_README_UPROBE_REF_CTR,
>  	FTRACE_README_USER_ACCESS,
> +	FTRACE_README_MULTIPROBE_EVENT,
>  	FTRACE_README_END,
>  };
>  
> @@ -1020,6 +1021,7 @@ static struct {
>  	DEFINE_TYPE(FTRACE_README_KRETPROBE_OFFSET, "*place (kretprobe): *"),
>  	DEFINE_TYPE(FTRACE_README_UPROBE_REF_CTR, "*ref_ctr_offset*"),
>  	DEFINE_TYPE(FTRACE_README_USER_ACCESS, "*[u]<offset>*"),
> +	DEFINE_TYPE(FTRACE_README_MULTIPROBE_EVENT, "*Create/append/*"),
>  };
>  
>  static bool scan_ftrace_readme(enum ftrace_readme type)
> @@ -1085,3 +1087,8 @@ bool user_access_is_supported(void)
>  {
>  	return scan_ftrace_readme(FTRACE_README_USER_ACCESS);
>  }
> +
> +bool multiprobe_event_is_supported(void)
> +{
> +	return scan_ftrace_readme(FTRACE_README_MULTIPROBE_EVENT);
> +}
> diff --git a/tools/perf/util/probe-file.h b/tools/perf/util/probe-file.h
> index 986c1c94f64f..850d1b52d60a 100644
> --- a/tools/perf/util/probe-file.h
> +++ b/tools/perf/util/probe-file.h
> @@ -71,6 +71,7 @@ bool probe_type_is_available(enum probe_type type);
>  bool kretprobe_offset_is_supported(void);
>  bool uprobe_ref_ctr_is_supported(void);
>  bool user_access_is_supported(void);
> +bool multiprobe_event_is_supported(void);
>  #else	/* ! HAVE_LIBELF_SUPPORT */
>  static inline struct probe_cache *probe_cache__new(const char *tgt __maybe_unused, struct nsinfo *nsi __maybe_unused)
>  {

-- 

- Arnaldo