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From: Christoph Hellwig <hch@infradead.org>
To: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
	Jens Axboe <jens.axboe@oracle.com>
Subject: Re: [patch 4/4] Port of blktrace to the Linux Kernel Markers.
Date: Thu, 30 Aug 2007 18:21:28 +0100	[thread overview]
Message-ID: <20070830172128.GA14460@infradead.org> (raw)
In-Reply-To: <20070827160710.807499112@polymtl.ca>

On Mon, Aug 27, 2007 at 12:05:44PM -0400, Mathieu Desnoyers wrote:
> Here is the first stage of a port of blktrace to the Linux Kernel Markers. The
> advantage of this port is that it minimizes the impact on the running when
> blktrace is not active.
> 
> A few remarks : this patch has the positive effect of removing some code
> from the block io tracing hot paths, minimizing the i-cache impact in a
> system where the io tracing is compiled in but inactive.
> 
> It also moves the blk tracing code from a header (and therefore from the
> body of the instrumented functions) to a separate C file.
> 
> There, as soon as one device has to be traced, all devices have to
> execute the tracing function call when they pass by the instrumentation site.
> This is slower than the previous inline function which tested the condition
> quickly.
> 
> It does not make the code smaller, since I left all the specialized
> tracing functions for requests, bio, generic, remap, which would go away
> once a generic infrastructure is in place to serialize the information
> passed to the marker. This is mostly why I consider it as a step towards the
> full improvements that could bring the markers.

I like this as it moves the whole tracing code out of line.  It would
be nice if we could make blktrace a module with this, but we'd need
to change the interface away from an ioctl on the block device for that.

Btw, something that really shows here and what I noticed in my sputrace
aswell is that there is a lot of boilerplate code due to the varargs
trace handlers.  We really need some way to auto-generate the boilerplate
for the trace function to avoid coding this up everywhere.

  reply	other threads:[~2007-08-30 17:21 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-08-27 16:05 [patch 0/4] " Mathieu Desnoyers
2007-08-27 16:05 ` [patch 1/4] Linux Kernel Markers - Architecture Independent Code Mathieu Desnoyers
2007-08-27 16:05 ` [patch 2/4] Linux Kernel Markers - Add kconfig menus for the marker code Mathieu Desnoyers
2007-08-27 16:05 ` [patch 3/4] Linux Kernel Markers - Documentation Mathieu Desnoyers
2007-08-27 16:05 ` [patch 4/4] Port of blktrace to the Linux Kernel Markers Mathieu Desnoyers
2007-08-30 17:21   ` Christoph Hellwig [this message]
2007-08-30 18:37     ` Mathieu Desnoyers
2007-08-30 17:12 ` [patch 0/4] " Christoph Hellwig
2007-08-31  1:16   ` Andrew Morton
  -- strict thread matches above, loose matches on Subject: below --
2007-09-18 21:13 [patch 0/4] Linux Kernel Markers for 2.6.23-rc6-mm1 Mathieu Desnoyers
2007-09-18 21:13 ` [patch 4/4] Port of blktrace to the Linux Kernel Markers Mathieu Desnoyers
2007-09-21  1:03   ` Steven Rostedt
2007-09-21 13:46     ` Mathieu Desnoyers
2007-09-17 18:46 [patch 0/4] " Mathieu Desnoyers
2007-09-17 18:46 ` [patch 4/4] Port of blktrace to the " Mathieu Desnoyers
2007-08-20 20:27 [patch 0/4] " Mathieu Desnoyers
2007-08-20 20:27 ` [patch 4/4] Port of blktrace to the " Mathieu Desnoyers
2007-08-12 15:10 [patch 0/4] " Mathieu Desnoyers
2007-08-12 15:10 ` [patch 4/4] Port of blktrace to the " Mathieu Desnoyers
2007-07-14  1:29 [patch 0/4] " Mathieu Desnoyers
2007-07-14  1:29 ` [patch 4/4] Port of blktrace to the " Mathieu Desnoyers
2007-07-03 17:08 [patch 0/4] " Mathieu Desnoyers
2007-07-03 17:08 ` [patch 4/4] Port of blktrace to the " Mathieu Desnoyers

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