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Date: Fri, 11 Sep 2009 12:03:30 -0400 From: Masami Hiramatsu <mhiramat@...hat.com> To: Frederic Weisbecker <fweisbec@...il.com> CC: Steven Rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...e.hu>, lkml <linux-kernel@...r.kernel.org>, Ananth N Mavinakayanahalli <ananth@...ibm.com>, Andi Kleen <ak@...ux.intel.com>, Christoph Hellwig <hch@...radead.org>, "Frank Ch. Eigler" <fche@...hat.com>, "H. Peter Anvin" <hpa@...or.com>, Jason Baron <jbaron@...hat.com>, Jim Keniston <jkenisto@...ibm.com>, "K.Prasad" <prasad@...ux.vnet.ibm.com>, Lai Jiangshan <laijs@...fujitsu.com>, Li Zefan <lizf@...fujitsu.com>, Peter Zijlstra <peterz@...radead.org>, Srikar Dronamraju <srikar@...ux.vnet.ibm.com>, Tom Zanussi <tzanussi@...il.com>, systemtap <systemtap@...rces.redhat.com>, DLE <dle-develop@...ts.sourceforge.net> Subject: Re: [PATCH tracing/kprobes 0/7] tracing/kprobes: kprobe-based event tracer update and perf support Frederic Weisbecker wrote: > On Thu, Sep 10, 2009 at 07:52:58PM -0400, Masami Hiramatsu wrote: >> Hi Frederic, >> >> This series fixes bugs and upgrades kprobe-based event tracer >> as a dynamic event tracer on ftrace/perf tools. This also enhances >> tracer output format to show each argument name and event name on >> each entry. >> >> With this series, users can add trace events dynamically on ftrace >> and use those events with perf tools as below. >> >> (Step.1) Define new events under new group >> >> $ echo p:mygroup/myprobe do_sys_open dfd=a0 filename=a1 flags=a2 mode=a3 \ >> > /debug/tracing/kprobes_events >> $ echo r:mygroup/myretprobe do_sys_open rv>> /debug/tracing/kprobes_events >> $ cat /debug/tracing/kprobes_events >> p:myprobe do_sys_open+0 dfd=a0 filename=a1 flags=a2 mode=a3 >> r:myretprobe do_sys_open+0 rv=rv >> >> (You can see that each argument has its name.) >> >> >> (Step.2) Perf shows new events >> >> $ perf list >> ... >> mygroup:myretprobe [Tracepoint event] >> mygroup:myprobe [Tracepoint event] >> ... >> >> >> (Step.3) Record events with perf >> >> $ perf record -f -e mygroup:myprobe:record -F 1 -a ls >> ... >> [ perf record: Captured and wrote 0.081 MB perf.data (~3544 samples) ] >> >> >> (Step.4) Perf trace shows the result >> >> $ perf trace >> version = 0.5 >> perf-1405 [000] 0.000000: myprobe: (c04b0a5c) dfd=ffffff9c filename=810d3f7 flags=98800 mode=1 >> perf-1405 [000] 0.000000: myprobe: (c04b0a5c) dfd=ffffff9c filename=bff7650c flags=8000 mode=1b6 >> perf-1405 [000] 0.000000: myprobe: (c04b0a5c) dfd=ffffff9c filename=bff7650c flags=98800 mode=bff7450c >> perf-1405 [000] 0.000000: myprobe: (c04b0a5c) dfd=ffffff9c filename=bff7650c flags=8000 mode=1b6 > > > Nice! > > May be another step in the todo-list that would be nice: define the format > for a type. Like it's done from ftrace events. Thanks! BTW, I'm not sure what the type means. Each event already has its own event ID and event_call. Could you tell me which part of ftrace I should refer to ? >> >> >> (Step.5) You can also use return probes. >> >> $ perf record -f -e mygroup:myretprobe:record -F 1 -a ls >> ... >> [ perf record: Captured and wrote 0.081 MB perf.data (~3544 samples) ] >> $ perf trace >> version = 0.5 >> perf-1408 [000] 0.000000: myretprobe: (c04b0a5c<- c04b0b7d) rv=b >> perf-1408 [000] 0.000000: myretprobe: (c04b0a5c<- c04b0b7d) rv=c >> perf-1408 [000] 0.000000: myretprobe: (c04b0a5c<- c04b0b7d) rv=d >> perf-1408 [000] 0.000000: myretprobe: (c04b0a5c<- c04b0b7d) rv=c >> >> >> TODO: >> - Implement perf kprobe command to help defining new probes. > > > > Yeah! > > I wonder what could be the best workflow to use it. > > Imagine the following steps: > > - perf kprobe = define kprobes using C expression > - perf record -e our_kprobes > - perf trace > > That's way too much. > Especially it's sad to be forced to define a kprobe, then > get back its name, use it with record, and eventually > unsheathe perf trace. > > I guess we should choose between the low level, very granular > but uninviting method "kprobe + record + trace" and also an all > in one quick approach. > > And that could be chosen from perf kprobe: > > Low level: > > perf kprobe --define-only [-p|-r] [probe_name] -a1 [arg1] -a2 [arg2] \ > --format="%s %...." > > perf record -e kprobes:probe_name > perf trace > > Quick: > > perf kprobe -p probe_name -a1 ..... cmdline| -a > > And after the profiled task is finished, it could launch perf trace > by itself (or wait for a Ctrl + C if -a/wide profiling) Another thought: expand record subcommand. perf record -E "p|r:probe_name,place,arg1,arg2..." perf trace And kprobe accept multiple definitions perf kprobe -E "p|r:probe_name,place,arg1,arg2..." -E ... Thank you, -- Masami Hiramatsu Software Engineer Hitachi Computer Products (America), Inc. Software Solutions Division e-mail: mhiramat@...hat.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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