[Ksummit-2012-discuss] Topic proposal: Finding and eliminating kernel work creation schemes

Tim Bird tim.bird at am.sony.com
Tue Jun 19 21:49:05 UTC 2012

On 06/19/2012 12:39 AM, James Bottomley wrote:
> On Mon, 2012-06-18 at 18:07 -0700, Tim Bird wrote:
>> More concretely, we have a camera with 32M of RAM, where 16M is
>> normally allocated to Linux, and 16M to the image sensor.
>> During bootup, 8M or 16M of that second pool are made
>> available to Linux to  improve boot time, and then removed
>> from Linux for use by the camera after boot.
> So this would be an interesting case to try with and without
> CONFIG_HOTPLUG.  I'm not proposing to remove __init and __exit, and I
> suspect you're getting most of your free memory after boot from __init,
> but it would be useful to validate.

I have to admit that I'm not familiar with all of
the annotations and checks associated with CONFIG_HOTPLUG.
I'll try to find some time to see what the size
differences are for some of our builds.

>> Recently, I've been doing some research on exactly this.   That is,
>> using automation and annotations outside the source code to remove
>> unneeded bits.  I don't know if I'll have any results to show by
>> August  (if not, the project will likely have been canceled),
>> but if people are interested I can discuss what I'm doing
>> in a hallway track.
> So this too, would be useful.  The direction I'm trying to push us in is
> automated, so things like --gc-sections (when it works).  It would be
> useful to compare the two approaches and see if there is any additional
> benefit from the annotation approach ... and whether it's worth the
> hassle of trying to preserve the annotations.

Indeed. One of the critical issues is whether annotations kept
separate from the source will be maintainable That's one thing
I hope to look at, by checking whether the annotations I have in
mind will work over long spans of kernel versions.
 -- Tim

Tim Bird
Architecture Group Chair, CE Workgroup of the Linux Foundation
Senior Staff Engineer, Sony Network Entertainment

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