[alsa-devel] Audio Mini Summit 2015, 8th October, Dublin

[Jie, Yang]

Hi all,

I have done some investigation on LTO usage and current status, summarize as below:

1. LTO is still only an experimental feature and not accepted by upstream yet;
2. to enable LTO, we need apply 20+ patches from Andi Kleen's github repo;
3. we need at least 4GB(8GB+ may be better) RAM for LTO kernel building, and using gcc 4.9+(maybe gcc rebuild needed);
4. kernel building may take much longer time, A few kernel features are currently incompatible with LTO.

So my conclusion on this is: LTO is still on experimental stage, we can try use it for specific customer project but not the goal of upstream yet; 
BTW, LTO is a kernel general feature, there is no help for upstream ALSA specific tinification to try on it. 

References:
https://github.com/andikleen/linux-misc/blob/lto-4.0/Documentation/lto-build
http://www.halobates.de/kernel-lto.pdf

thanks,
~Keyon

> -----Original Message-----
> From: Jie, Yang
> Sent: Tuesday, October 13, 2015 9:34 AM
> To: Jaroslav Kysela; alsa-devel at alsa-project.org
> Subject: RE: [alsa-devel] Audio Mini Summit 2015, 8th October, Dublin
> 
> 
> Thanks for pointing out this, Takashi, Lars, and Jaroslav.
> 
> I will try this LTO firstly and see what will happen.
> 
> Thanks,
> ~Keyon
> 
> 
> > -----Original Message-----
> > From: alsa-devel-bounces at alsa-project.org [mailto:alsa-devel-
> > bounces at alsa-project.org] On Behalf Of Jaroslav Kysela
> > Sent: Tuesday, October 13, 2015 12:21 AM
> > To: alsa-devel at alsa-project.org
> > Subject: Re: [alsa-devel] Audio Mini Summit 2015, 8th October, Dublin
> >
> > Dne 12.10.2015 v 17:54 Lars-Peter Clausen napsal(a):
> >
> > > E.g. I'd consider parameter refining a vital part of ALSA and the
> > > core functionality of it is rather compact. But it provides a lot of
> > > helper functions of which only some are going to be used if you
> > > built a reduced kernel. So rather then completely disabling
> > > parameter refining use LTO to remove the unused helper functions.
> >
> > I agree. It sounds like perfect solution for optimized kernel builds.
> >
> > 					Jaroslav
> >
> > --
> > Jaroslav Kysela <perex at perex.cz>
> > Linux Sound Maintainer; ALSA Project; Red Hat, Inc.
> > _______________________________________________
> > Alsa-devel mailing list
> > Alsa-devel at alsa-project.org
> > http://mailman.alsa-project.org/mailman/listinfo/alsa-devel