Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758150AbZGGV7A (ORCPT ); Tue, 7 Jul 2009 17:59:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754138AbZGGV6u (ORCPT ); Tue, 7 Jul 2009 17:58:50 -0400 Received: from mx2.redhat.com ([66.187.237.31]:38594 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752868AbZGGV6t (ORCPT ); Tue, 7 Jul 2009 17:58:49 -0400 Message-ID: <4A53C59A.3060706@redhat.com> Date: Tue, 07 Jul 2009 18:00:58 -0400 From: Masami Hiramatsu User-Agent: Thunderbird 2.0.0.21 (X11/20090320) MIME-Version: 1.0 To: Frederic Weisbecker CC: Ingo Molnar , Steven Rostedt , lkml , systemtap , kvm , DLE , Ananth N Mavinakayanahalli , Christoph Hellwig , Tom Zanussi Subject: Re: [PATCH -tip -v10 7/7] tracing: add kprobe-based event tracer References: <20090701010838.32547.62843.stgit@localhost.localdomain> <20090701010923.32547.74203.stgit@localhost.localdomain> <20090707073103.GA6173@nowhere> <4A53A830.3000305@redhat.com> <20090707202008.GE6184@nowhere> <4A53B338.4060803@redhat.com> <20090707205851.GF6184@nowhere> <4A53BEAD.7030404@redhat.com> <20090707213447.GC7412@nowhere> <4A53C144.20807@redhat.com> In-Reply-To: <4A53C144.20807@redhat.com> X-Enigmail-Version: 0.95.7 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3800 Lines: 102 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/