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Re: [RFC][BUG] tracer: Fails to work

From Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Newsgroups linux.kernel
Subject Re: [RFC][BUG] tracer: Fails to work
Date 2016-01-28 15:40 +0100
Message-ID <qVVTQ-4Lm-13@gated-at.bofh.it> (permalink)
References <qVPOq-x3-5@gated-at.bofh.it> <qVUXM-43r-17@gated-at.bofh.it> <qVVh9-4b8-29@gated-at.bofh.it>
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----- On Jan 28, 2016, at 8:57 AM, Peter Zijlstra peterz@infradead.org wrote:

> On Thu, Jan 28, 2016 at 01:38:00PM +0000, Mathieu Desnoyers wrote:
> 
>> Thoughts ?
> 
> So ideally dumping the trace data would not depend on any of that,
> because I can break it all :-)
> 
> Not being able to access the trace data completely and utterly defeats
> the purpose of having a tracer in the first place.

One item I have on my todo list is to allow mapping
the tracer buffers (lttng in my case) onto RAM that
persists across reboots/kexec using dax and the pmem
driver. Since the original system is clearly inactive
after a reboot, we can read the buffers from memory
without caring about synchronization.

That would be one possible way of handling your
snapshot-of-buggy-kernel-trace-buffers use-case.

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com

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Thread

[RFC][BUG] tracer: Fails to work Peter Zijlstra <peterz@infradead.org> - 2016-01-28 09:10 +0100
  Re: [RFC][BUG] tracer: Fails to work Mathieu Desnoyers <mathieu.desnoyers@efficios.com> - 2016-01-28 14:40 +0100
    Re: [RFC][BUG] tracer: Fails to work Peter Zijlstra <peterz@infradead.org> - 2016-01-28 15:00 +0100
      Re: [RFC][BUG] tracer: Fails to work Steven Rostedt <rostedt@goodmis.org> - 2016-01-28 15:20 +0100
      Re: [RFC][BUG] tracer: Fails to work Mathieu Desnoyers <mathieu.desnoyers@efficios.com> - 2016-01-28 15:40 +0100
        Re: [RFC][BUG] tracer: Fails to work Peter Zijlstra <peterz@infradead.org> - 2016-01-28 15:50 +0100
          Re: [RFC][BUG] tracer: Fails to work Mathieu Desnoyers <mathieu.desnoyers@efficios.com> - 2016-01-28 16:00 +0100
            Re: [RFC][BUG] tracer: Fails to work Peter Zijlstra <peterz@infradead.org> - 2016-01-28 16:40 +0100
              Re: [RFC][BUG] tracer: Fails to work Steven Rostedt <rostedt@goodmis.org> - 2016-01-28 17:00 +0100

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