Re: [PROPOSAL] Compressed printk messages


Jean-Christophe PLAGNIOL-VILLARD
 

On 22:31 Wed 02 Oct , Bird, Tim wrote:
; Summary: Compressed printk messages
; Proposer: Tim Bird - Sony Mobile Communications

== Description ==
Attempts have been made in the past to compress printk messages to save kernel
runtime footprint. There is an option to disable all printks, but many embedded
developers do not use it, even when they find the space savings attractive, because
they still would like to see kernel debug messages.

This project would consist of researching mechanisms that could be used
to automatically (at compile-time) compress the kernel's printk messages,
and transparently expand them at runtime.

The goal would be to have no user-visible change in behaviour for the
kernel, as well as no required developer-visible changes in the source code.
Probably, a new kernel option would be used to control this
feature.

The work would involve parsing the kernel source code, extracting
the messages (and possibly replacing them in source, during the compilation),
compressing them, and replacing the original strings with references to
the compressed messages (in a way that the messages can be uncompressed
transparently at runtime.)

=== Miscelaneous issues ===
There may be an issue with finding all kernel messages, due to the number
of macros (probably in the hundreds) that are used to wrap printks.
This feature might still be useful, even if not all kernel messages
could be converted, as long as significant size savings were made
available by using the feature. Significant size savings would be
on the order of 50K to 100K.

There might also be some benefit from message consolidation. (I don't know
if the compiler already coalesces identical strings, but this system should
be able to.)
I'm intresseteing in it

we could use this too on barebox

Best Regards,
J.

== Related work ==
* Timothy Miller did some work on this in 2003
** See http://lwn.net/Articles/28935/
** See https://lkml.org/lkml/2003/6/6/207
* See also some ideas here:
** http://selenic.com/pipermail/linux-tiny/2005-June/000208.html

== Scope ==
Unknown - 4 to 8 weeks?

== Contractor Candidates ==
None yet.

== Comments ==
This project was proposed in 2012, but not sponsored that year.

[[Category:Project proposals 2012]]
[[Category:Project proposals 2013]]
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