linux-kernel - Re: [PATCH 10/15] ftrace: fix event alignment: jbd2:*

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Message-ID: <1299631305.20306.113.camel@gandalf.stny.rr.com>
Date:	Tue, 08 Mar 2011 19:41:45 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Ted Ts'o <tytso@....edu>
Cc:	David Sharp <dhsharp@...gle.com>, linux-kernel@...r.kernel.org,
	mrubin@...gle.com, Jiaying Zhang <jiayingz@...gle.com>
Subject: Re: [PATCH 10/15] ftrace: fix event alignment: jbd2:*

On Tue, 2011-03-08 at 19:31 -0500, Ted Ts'o wrote:
> On Tue, Mar 08, 2011 at 07:03:25PM -0500, Steven Rostedt wrote:
> > Now I know why I was so late at adding this. I was waiting for
> > Acked-bys ;)
> > 
> > On Fri, 2010-12-03 at 20:52 -0500, Steven Rostedt wrote:
> > > [ Ccing Ted for Acked-by ]
> > 
> > Ted, Ping?
> 
> A month or two ago I did an analysis using the pahole binary (part of
> the 'dwarves' package in Debian/Ubuntu) and noticed many more
> structures that were flagged as having 'holes' where there were
> optimization opportunities.
> 
> In addition, (in an interesting example of synchronicity) just this
> afternoon, I had talked to Jiaying about a further optimization of the
> ext4 trace header files, since she pointed out to me that the 'perf'
> binary can actually handle the MAJOR() and MINOR() macros.  So we can
> replace 8 bytes of "int major, minor", with a 4 byte dev_t, and save
> another 4 bytes (assuming we can move the structure elements around so
> we can save a full 8 bytes to avoid structure padding).
> 
> Jiaying was also going to send some patches to add some additional
> tracepoints to the upstream kernel.
> 
> So probably the best thing to do at this point is to drop the ext4 and
> jbd2 patches, since Jiaying is about to send me patches that to handle
> these optimizations plus some further ones --- and add some additional
> tracepoints.  Getting one patch from her that I'll feed in via the
> ext4 tree probably will be much simpler than coordinating patches to
> the same file from two different trees.

OK, thanks for the explanation. I'll go ahead and drop those two patches
from my queue.

-- Steve


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