linux-kernel - Re: blktrace ftrace plugin, was Re: Receive side performance issue with multi-10-GigE and NUMA

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Message-ID: <20090827135507.GL5255@ghostprotocols.net>
Date:	Thu, 27 Aug 2009 10:55:07 -0300
From:	Arnaldo Carvalho de Melo <acme@...hat.com>
To:	Jens Axboe <jens.axboe@...cle.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Li Zefan <lizf@...fujitsu.com>,
	Christoph Hellwig <hch@...radead.org>, rostedt@...dmis.org,
	fweisbec@...il.com, acme@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: blktrace ftrace plugin, was Re: Receive side performance issue
	with multi-10-GigE and NUMA

Em Thu, Aug 27, 2009 at 11:14:54AM +0200, Jens Axboe escreveu:
> On Thu, Aug 27 2009, Ingo Molnar wrote:
> > 
> > * Jens Axboe <jens.axboe@...cle.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?
> 
> Of course, we have to retain the ioctl/relayfs interface, it's been in
> use for years. Keeping those out of the other trace/ bits sounds sane.

Yeah, I wonder tho if we couldn't somehow use the ring buffer
infrastructure in such a way as to provide the debugfs visible interface
provided by relayfs, IIRC systemtap is doing such a move too.

- Arnaldo
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