Re: Tracing configuration review

[Li Zefan]

Pekka Enberg wrote:
> On Tue, May 25, 2010 at 11:13 PM, Frederic Weisbecker
> <fweisbec@xxxxxxxxx> 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.

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