From: Masami Hiramatsu <mhiramat@redhat.com>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>,
lkml <linux-kernel@vger.kernel.org>,
systemtap <systemtap@sources.redhat.com>,
kvm <kvm@vger.kernel.org>,
DLE <dle-develop@lists.sourceforge.net>,
Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
Christoph Hellwig <hch@infradead.org>,
Tom Zanussi <tzanussi@gmail.com>
Subject: Re: [PATCH -tip -v10 7/7] tracing: add kprobe-based event tracer
Date: Tue, 07 Jul 2009 21:58:00 -0000 [thread overview]
Message-ID: <4A53C59A.3060706@redhat.com> (raw)
In-Reply-To: <4A53C144.20807@redhat.com>
Masami Hiramatsu wrote:
> Frederic Weisbecker wrote:
>> On Tue, Jul 07, 2009 at 05:31:25PM -0400, Masami Hiramatsu wrote:
>>> Frederic Weisbecker wrote:
>>>> On Tue, Jul 07, 2009 at 04:42:32PM -0400, Masami Hiramatsu wrote:
>>>>> Frederic Weisbecker wrote:
>>>>>> On Tue, Jul 07, 2009 at 03:55:28PM -0400, Masami Hiramatsu wrote:
>>>>>>> Frederic Weisbecker wrote:
>>>>>>>>> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
>>>>>>>>> index 206cb7d..65945eb 100644
>>>>>>>>> --- a/kernel/trace/trace.h
>>>>>>>>> +++ b/kernel/trace/trace.h
>>>>>>>>> @@ -45,6 +45,8 @@ enum trace_type {
>>>>>>>>> TRACE_POWER,
>>>>>>>>> TRACE_BLK,
>>>>>>>>> TRACE_KSYM,
>>>>>>>>> + TRACE_KPROBE,
>>>>>>>>> + TRACE_KRETPROBE,
>>>>>>>>>
>>>>>>>>> __TRACE_LAST_TYPE,
>>>>>>>>> };
>>>>>>>>> @@ -227,6 +229,22 @@ struct trace_ksym {
>>>>>>>>> char ksym_name[KSYM_NAME_LEN];
>>>>>>>>> char p_name[TASK_COMM_LEN];
>>>>>>>>> };
>>>>>>>>> +#define TRACE_KPROBE_ARGS 6
>>>>>>>>> +
>>>>>>>>> +struct kprobe_trace_entry {
>>>>>>>>> + struct trace_entry ent;
>>>>>>>>> + unsigned long ip;
>>>>>>>>> + int nargs;
>>>>>>>>> + unsigned long args[TRACE_KPROBE_ARGS];
>>>>>>>> I see that you actually make use of arg as a dynamic sizeable
>>>>>>>> array.
>>>>>>>> For clarity, args[TRACE_KPROBE_ARGS] could be args[0].
>>>>>>>>
>>>>>>>> It's just a neat and wouldn't affect the code nor the data
>>>>>>>> but would be clearer for readers of that code.
>>>>>>> Hmm. In that case, I think we'll need a new macro for field
>>>>>>> definition, like TRACE_FIELD_ZERO(type, item).
>>>>>> You mean that for trace_define_field() to describe fields of events?
>>>>>> Actually the fields should be defined dynamically depending on how
>>>>>> is built the kprobe event (which arguments are requested, how many,
>>>>>> etc..).
>>>>> Yeah, if you specified a probe point with its event name, the tracer
>>>>> will make a corresponding event dynamically. There are also anonymous
>>>>> probes which don't have corresponding events. For those anonymous
>>>>> probes, I need to define two generic event types(kprobe and kretprobe).
>>>>>
>>>>> Thank you,
>>>> Ok. Btw, why do you need to define those two anonymous events?
>>>> Actually your event types are always dynamically created.
>>>> Those you defined through TRACE_FORMAT_EVENT are only "ghost events",
>>>> they only stand there as a abstract pattern, right?
>>>>
>>> Not always created.
>>>
>>> Below command will create an event "event1";
>>> p probe_point:event1 a1 a2 a3 ... > /debug/tracing/kprobe_events
>>>
>>> But next command doesn't create.
>>> p probe_point a1 a2 a3 ... > /debug/tracing/kprobe_events
>>
>> Aah, ok.
>>
>>
>>> This just inserts a kprobe to probe_point. the advantage of this
>>> "simple" command is that you never be annoyed by making different
>>> name for new events :-)
>>
>> Indeed.
>> But speaking about that, may be you could dynamically create a name
>> following this simple model: func+offset
hmm, and we have two probe types, p(robe) and r(et probe).
so, event name should be type@func+offset or type@address.
>> Unless we can set several kprobes on the exact same address?
>
> Actually, we can...
> I thought that someone might want to insert events in the same
> address for retrieving more than 6 arguments.
Anyway, I can improve the interface according to user's voice.
If you have good idea, I'm happy to hear that:-)
Thank you,
--
Masami Hiramatsu
Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division
e-mail: mhiramat@redhat.com
next prev parent reply other threads:[~2009-07-07 21:58 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-07-01 1:05 [PATCH -tip -v10 0/7] tracing: kprobe-based event tracer and x86 instruction decoder Masami Hiramatsu
2009-07-01 1:05 ` [PATCH -tip -v10 1/7] x86: instruction decoder API Masami Hiramatsu
2009-07-01 1:05 ` [PATCH -tip -v10 2/7] x86: x86 instruction decoder build-time selftest Masami Hiramatsu
2009-07-01 1:06 ` [PATCH -tip -v10 4/7] kprobes: cleanup fix_riprel() using insn decoder on x86 Masami Hiramatsu
2009-07-01 1:06 ` [PATCH -tip -v10 7/7] tracing: add kprobe-based event tracer Masami Hiramatsu
[not found] ` <20090707073103.GA6173@nowhere>
2009-07-07 19:52 ` Masami Hiramatsu
2009-07-07 20:20 ` Frederic Weisbecker
2009-07-07 20:39 ` Masami Hiramatsu
2009-07-07 20:59 ` Frederic Weisbecker
2009-07-07 21:28 ` Masami Hiramatsu
2009-07-07 21:35 ` Frederic Weisbecker
2009-07-07 21:39 ` Masami Hiramatsu
2009-07-07 21:58 ` Masami Hiramatsu [this message]
2009-07-01 1:06 ` [PATCH -tip -v10 3/7] kprobes: checks probe address is instruction boudary on x86 Masami Hiramatsu
2009-07-01 1:17 ` [PATCH -tip -v10 5/7] x86: add pt_regs register and stack access APIs Masami Hiramatsu
2009-07-06 1:42 ` Frederic Weisbecker
2009-07-06 14:37 ` Andi Kleen
2009-07-06 19:25 ` Masami Hiramatsu
2009-07-06 20:06 ` Andi Kleen
2009-07-07 0:04 ` Masami Hiramatsu
2009-07-01 1:17 ` [PATCH -tip -v10 6/7] tracing: ftrace dynamic ftrace_event_call support Masami Hiramatsu
2009-07-06 2:00 ` Frederic Weisbecker
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