From: Alexei Starovoitov <ast-uqk4Ao+rVK5Wk0Htik3J/w@public.gmane.org>
To: Steven Rostedt <rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org>
Cc: Ingo Molnar <mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Namhyung Kim <namhyung-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Arnaldo Carvalho de Melo
<acme-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
Jiri Olsa <jolsa-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Masami Hiramatsu
<masami.hiramatsu.pt-FCd8Q96Dh0JBDgjK7y7TUQ@public.gmane.org>,
Linux API <linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Network Development
<netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Linus Torvalds
<torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
"Eric W. Biederman"
<ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
Subject: Re: [PATCH v3 linux-trace 1/8] tracing: attach eBPF programs to tracepoints and syscalls
Date: Sat, 14 Feb 2015 17:54:18 -0500 [thread overview]
Message-ID: <CAMEtUuzP9RBaaWr7d1qkFB_fukK44hALvFyxY=x95TKqw8q-Jg@mail.gmail.com> (raw)
On Wed, Feb 11, 2015 at 7:51 AM, Steven Rostedt <rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org> wrote:
> On Tue, 10 Feb 2015 22:33:05 -0800
> Alexei Starovoitov <ast-uqk4Ao+rVK5Wk0Htik3J/w@public.gmane.org> wrote:
>
>
>> fair enough.
>> Something like TRACE_MARKER(arg1, arg2) that prints
>> it was hit without accessing the args would be enough.
>> Without any args it is indeed a 'fast kprobe' only.
>> Debug info would still be needed to access
>> function arguments.
>> On x64 function entry point and x64 abi make it easy
>> to access args, but i386 or kprobe in the middle
>> lose visibility when debug info is not available.
>> TRACE_MARKER (with few key args that function
>> is operating on) is enough to achieve roughly the same
>> as kprobe without debug info.
>
> Actually, what about a TRACE_EVENT_DEBUG(), that has a few args and
> possibly a full trace event layout.
>
> The difference would be that the trace events do not show up unless you
> have "trace_debug" on the command line. This should prevent
> applications from depending on them.
>
> I could even do the nasty dmesg output like I do with trace_printk()s,
> that would definitely keep a production kernel from adding it by
> default.
>
> When trace_debug is not there, the trace points could still be accessed
> but perhaps only via bpf, or act like a simple trace marker.
I think that is a great idea!
Makes it clear that all prints are for debugging and
no abi guarantees.
> Note, if you need ids, I rather have them in another directory than
> tracefs. Make a eventfs perhaps that holds these. I rather keep tracefs
> simple.
indeed. makes sense. no reason to burn fs memory just
to get an id from name. may be perf_event api can be
extended to lookup id from name. I think perf will benefit as well.
next reply other threads:[~2015-02-14 22:54 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-14 22:54 Alexei Starovoitov [this message]
-- strict thread matches above, loose matches on Subject: below --
2015-02-23 18:55 [PATCH v3 linux-trace 1/8] tracing: attach eBPF programs to tracepoints and syscalls Alexei Starovoitov
2015-02-14 23:02 Alexei Starovoitov
2015-02-14 22:48 Alexei Starovoitov
2015-02-11 6:33 Alexei Starovoitov
[not found] ` <CAMEtUuxizvHF09y_vU-c+L=n16tqWDqJPTybGB1a_OqN7p+jsA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-02-11 12:51 ` Steven Rostedt
2015-02-11 3:04 Alexei Starovoitov
[not found] ` <CAMEtUuy+B9aXP-8m7tA6aNxnS4SKRhMpfGEdWMcbxbj7ggOATw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-02-11 4:31 ` Steven Rostedt
2015-02-11 0:22 Alexei Starovoitov
[not found] ` <CAMEtUuzY_Po=WtFEFg1aqzJ8dEF4rHGcWDsaS44KYgACMNPPgA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-02-11 0:50 ` Steven Rostedt
2015-02-11 9:45 ` Peter Zijlstra
2015-02-11 10:15 ` Peter Zijlstra
2015-02-12 4:58 ` Hekuang
2015-02-11 9:33 ` Peter Zijlstra
2015-02-16 11:26 ` He Kuang
2015-02-10 19:53 Alexei Starovoitov
[not found] ` <CAMEtUuwAf4AFeWVEdJB4VQz_=2fWY=q8=rbkFg38rtVtNVCHxg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-02-10 21:53 ` Steven Rostedt
[not found] ` <20150210165359.34cc53d9-f9ZlEuEWxVcJvu8Pb33WZ0EMvNT87kid@public.gmane.org>
2015-02-11 10:28 ` Peter Zijlstra
2015-02-10 6:10 Alexei Starovoitov
[not found] ` <CAMEtUuztTca2jC9Su0YkTHEUHsD4p2PBRyukabrjGO0WfFzdfA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-02-10 13:05 ` Steven Rostedt
2015-02-10 5:51 Alexei Starovoitov
2015-02-10 12:27 ` Steven Rostedt
2015-02-10 3:45 [PATCH v3 linux-trace 0/8] tracing: attach eBPF programs to tracepoints/syscalls/kprobe Alexei Starovoitov
[not found] ` <1423539961-21792-1-git-send-email-ast-uqk4Ao+rVK5Wk0Htik3J/w@public.gmane.org>
2015-02-10 3:45 ` [PATCH v3 linux-trace 1/8] tracing: attach eBPF programs to tracepoints and syscalls Alexei Starovoitov
[not found] ` <1423539961-21792-2-git-send-email-ast-uqk4Ao+rVK5Wk0Htik3J/w@public.gmane.org>
2015-02-10 4:46 ` Steven Rostedt
2015-02-10 5:13 ` Steven Rostedt
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