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Date: Wed, 26 May 2010 15:20:16 +0800
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To: Pekka Enberg <penberg@cs.helsinki.fi>
CC: Frederic Weisbecker <fweisbec@gmail.com>,
       Chase Douglas <chase.douglas@canonical.com>,
       Prasad <prasad@linux.vnet.ibm.com>,
       Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>,
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       Steven Rostedt <rostedt@goodmis.org>, Ingo Molnar <mingo@redhat.com>,
       linux-kernel@vger.kernel.org
Subject: Re: Tracing configuration review
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Pekka Enberg wrote:
> On Tue, May 25, 2010 at 11:13 PM, Frederic Weisbecker
> <fweisbec@gmail.com> wrote:
>>> # CONFIG_KMEMTRACE is not set (Kconfig says N if unsure)
>> Deprecated. We have the kmem trace event that are a full replacement now.
>> Pekka, Gabriel, can we remove it now?
> 
> I don't think ftrace supports boot-time tracing which kmemtrace did.

We can do boot-time tracing by passing "trace_event=" kernel parameter.

By passing "ftrace=kmemtrace", kmemtrace can be started when
calling tracer_alloc_buffer(), which is an early_initcall.
While trace events are inititialized as a fs_initcall,  it can
be modified to an early_initcall.

Furthermore, I noticed the discussion on perf persistent events, which
seems to enable perf trace at boot time, so I think perf-kmem can take
advantage of this and will be a full-replacement of kmemtrace soon ?

> That said, I was probably the only one actually using the feature so
> maybe we can just nuke kmemtrace at this point...

If you agree on removing kmemtrace now, I'll re-send the patch.