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Date: Tue, 08 Nov 2011 16:08:09 -0800
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To: Arnaud Lacombe <lacombar@gmail.com>
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Cc: "K. Macy" <kmacy@freebsd.org>, Alan Cox <alc@rice.edu>,
	Andriy Gapon <avg@freebsd.org>,
	Attilio Rao <attilio@freebsd.org>, freebsd-current@freebsd.org,
	Benjamin Kaduk <kaduk@mit.edu>, Kostik Belousov <kostikbel@gmail.com>,
	Penta Upa <bsdboot@gmail.com>
Subject: Re: Using Instruction Pointer address in debug interfaces [Was: Re:
 vm_page_t related KBI [Was: Re: panic at vm_page_wire with FreeBSD
 9.0 Beta 3]]
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On 11/8/11 10:49 AM, Arnaud Lacombe wrote:
> Hi,
> To avoid future complaints about the fact that I would be only "talk"
> without "action", I did implement what I suggested above. As it is
> quite a large patch-set, I will not post it directly here, however, it
> is available on github:
>
> https://github.com/lacombar/freebsd/tree/master/topic/kern-lock-debug
>
> It convert a bunch of debug interface to use the caller instruction
> pointer, as well as a proof-of-concept teaching printf(9) to convert
> IP to symbol_name+offset.
>
> It translates in a direct saving of about +250kB on i386's GENERIC,
> just in kernel text size. Even the worst case, ie LOCK_DEBUG == 0,
> translates to a save of +80kB.
>
> Please note that this is still WIP code.

A couple of comments.
Firstly, the idea of a printf method to print the IP as symbol+offset 
is an interesting idea
that should be followed up in its own right.

However, (comment 2)  I would much rather file+line in this case.
I don't want to have the tools to decode the offset into a location in 
sources.

We have both systems in operation art work and I far prefer the latter.