[PATCH] D25766: [ELF] - Implemented --section-ordering-file option.

[Rui Ueyama via llvm-commits]

+tmsriram because he seems to have done something with
--section-ordering-file so he might have an expert's opinion about how much
it is useful/effective.

On Thu, Oct 20, 2016 at 8:48 AM, George Rimar <grimar at accesssoftek.com>
wrote:

> grimar added a comment.
>
> In https://reviews.llvm.org/D25766#574420, @davide wrote:
>
> > In https://reviews.llvm.org/D25766#574368, @ruiu wrote:
> >
> > > Is this effort coordinated with Davide?
> >
> >
> > Yes! Thanks George for taking care of this.
> >  BTW, I think the hard part of this feature is trying to evaluate and
> understand if it's worth it.
> >  You may want to do some benchmarking/write a systap/dtrace script to
> collect data and feed into the linker and make sure this has some real
> impact. I recommend to use bare metal for testing and not VM as the results
> might be unreliable.
> >  Rui, Rafael, what do you think?
>
>
> After today investigations I found next more or less known ways to produce
> such file.
>
> - First is use of valgring + icegrind plugin:
>
> https://blog.mozilla.org/tglek/2010/04/07/icegrind-valgrind-plugin-for-
> optimizing-cold-startup/
> https://glandium.org/blog/?p=1008
> Method looks a bit outdated though.
>
> - Use of function_reordering_plugin from gcc google branch (
> https://codereview.appspot.com/5124041, https://codereview.appspot.
> com/4802070/).
>
> As far I understand along with job it do, it also should produce
> final_layout.txt file where sections should be dumped in a correct order,
> and we should be able to reuse that file for LLD needs.
>
> - facebook/hhvm (https://github.com/facebook/hhvm/tree/master/hphp/tools/
> hfsort) has tools and scrips for generating sections ordering file for
> gold, though
>
> I am not sure how much easy can be to reuse it for any other applications.
>
> I am going to check gcc way tomorrow, it seems to me as most easy possible
> path.
>
>
> https://reviews.llvm.org/D25766
>
>
>
>
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