From: Namhyung Kim <namhyung@kernel.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
Ingo Molnar <mingo@elte.hu>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Anton Arapov <anton@redhat.com>, Frank Eigler <fche@redhat.com>,
Jiri Olsa <jolsa@redhat.com>, Josh Stone <jistone@redhat.com>,
Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
"Suzuki K. Poulose" <suzuki@in.ibm.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/1] (Was uprobes/perf: pre-filtering)
Date: Thu, 07 Feb 2013 15:01:28 +0900 [thread overview]
Message-ID: <87bobwslvr.fsf@sejong.aot.lge.com> (raw)
In-Reply-To: <20130206194218.GA11998@redhat.com> (Oleg Nesterov's message of "Wed, 6 Feb 2013 20:42:18 +0100")
Hi Oleg,
On Wed, 6 Feb 2013 20:42:18 +0100, Oleg Nesterov wrote:
> OK, builtin-record.c:record sets .target->uses_mmap == T, this is correct,
> we are going to use perf_mmap().
>
> But why do we need it? It is for perf_evlist__create_maps() to ensure we
> do not use cpu_map__dummy_new().
>
> But. Even if we use perf_mmap(), "event->cpu == -1 && !event->attr.inherit"
> is fine. And indeed, "perf record -e whatever -p1" creates a single counter
> with "cpu = -1" and this works. Because, damn, perf_evlist__config_attrs()
> notices "evlist->cpus->map[0] < 0" and sets "opts->no_inherit = true".
>
> But at the same time, this does not allow to do, say,
> "perf record -e whatever -C0 -p1". -C0 is simply ignored because when
> perf_evlist__create_maps() is called perf_target__has_task() == T due to "-p1".
>
> Not to mention, there is no way to trace init and the children it will
> fork...
>
> And otoh. "perf record -e whatever -i true" creates a counter for each
> cpu due to ->uses_mmap. This is suboptimal, but of course the hack like
>
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -1081,6 +1078,8 @@ int cmd_record(int argc, const char **argv, const char *prefix __maybe_unused)
> if (!argc && perf_target__none(&rec->opts.target))
> usage_with_options(record_usage, record_options);
>
> + rec->opts.target.uses_mmap = !rec->opts.no_inherit;
> +
> if (rec->force && rec->append_file) {
> ui__error("Can't overwrite and append at the same time."
> " You need to choose between -f and -A");
>
> should not be even discussed.
>
> And why opts->target.system_wide is only set by OPT_BOOLEAN("all-cpus") ?
> I meant, why I can't do "perf record -e whatever -C0" to create a "global"
> counter on CPU_0? This doesn't work because __cmd_record() sees !.system_wide
> and assumes we need perf_event__synthesize_thread_map() which silently fail.
>
> So I am sending a single patch to fix the problem which complicated my
> testing. It is trivial but I am not sure it correct, please review.
Yes, it's not clear how it handles above (-C0) case. I think it should
be treated as a system_wide mode like --all-cpus (-a). So we could set
->system_wide to true if -C is given and/or test perf_target__has_cpu()
for perf_event__synthesize_thread_map() or both.
Thanks,
Namhyung
next prev parent reply other threads:[~2013-02-07 6:01 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-04 19:02 [PATCH 0/7] uprobes/perf: pre-filtering Oleg Nesterov
2013-02-04 19:02 ` [PATCH 1/7] perf: Ensure we do not free event->parent before event Oleg Nesterov
2013-03-20 13:35 ` Jiri Olsa
2013-02-04 19:02 ` [PATCH 2/7] perf: Introduce hw_perf_event->tp_target and ->tp_list Oleg Nesterov
2013-02-11 9:44 ` Srikar Dronamraju
2013-02-04 19:02 ` [PATCH 3/7] uprobes: Introduce uprobe_apply() Oleg Nesterov
2013-02-11 9:43 ` Srikar Dronamraju
2013-02-04 19:02 ` [PATCH 4/7] uprobes/perf: Teach trace_uprobe/perf code to track the active perf_event's Oleg Nesterov
2013-02-11 9:45 ` Srikar Dronamraju
2013-02-04 19:02 ` [PATCH 5/7] uprobes/perf: Teach trace_uprobe/perf code to pre-filter Oleg Nesterov
2013-02-11 9:46 ` Srikar Dronamraju
2013-02-04 19:03 ` [PATCH 6/7] uprobes/perf: Teach trace_uprobe/perf code to use UPROBE_HANDLER_REMOVE Oleg Nesterov
2013-02-11 9:54 ` Srikar Dronamraju
2013-02-04 19:03 ` [PATCH 7/7] uprobes/perf: Avoid uprobe_apply() whenever possible Oleg Nesterov
2013-02-11 9:55 ` Srikar Dronamraju
2013-02-06 18:10 ` [PATCH 0/7] uprobes/perf: pre-filtering Oleg Nesterov
2013-02-06 19:42 ` [PATCH 0/1] (Was uprobes/perf: pre-filtering) Oleg Nesterov
2013-02-06 19:42 ` [PATCH 1/1] perf/tools: Fix "perf record -C... workload" behaviour Oleg Nesterov
2013-02-25 9:58 ` Jiri Olsa
2013-02-07 6:01 ` Namhyung Kim [this message]
2013-02-07 15:22 ` [PATCH 0/1] (Was uprobes/perf: pre-filtering) Oleg Nesterov
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