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SubjectRe: blktrace ftrace plugin, was Re: Receive side performance issue with multi-10-GigE and NUMA
Ingo Molnar wrote:
> * Jens Axboe <jens.axboe@oracle.com> wrote:
>
>> On Wed, Aug 26 2009, Christoph Hellwig wrote:
>>> On Wed, Aug 26, 2009 at 10:40:27PM +0200, Ingo Molnar wrote:
>>>> We are also converting non-trivial plugins to generic tracepoints. A
>>>> recent example are the system call tracepoints, but we also
>>>> converted blktrace and kmemtrace to generic tracepoints.
>>> On something semi-related: Any reason to keep the blktrace
>>> ftrace plugin around? I don't think there's much point in it.
>>> It only got added in 2.6.29, and all the blktrace tooling just
>>> uses the legacy ioctls. All new uses should just use the
>>> TRACE_EVENT output.
>> Lets kill it.
>
> Agreed.
>
> I think we should keep the relayfs and ioctl compatibility bits
> though: blktrace has a mature user-space environment with many
> years of installed base.
>
> We could even move those bits back to block/blktrace_compat.c or so
> (after the ftrace plugin bits are removed), to make sure it's nicely
> isolated.
>
> What do you think?
>

I'm all for removing the ftrace plugin. There're 2 concerns:

- dev_t info can't be recorded in some blk trace events. I think
this will change in the future when we can map a request_queue to
a unique device?

- Not all the output of ftrace plugin comes from tracepoints probing,
but via blk_add_trace_msg(), which directly writes a string into
ring buffer. I think they need to be converted to TRACE_EVENT.



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