Re: [PATCH] lto: Add __noreorder and mark initcalls __noreorder

From: Andrew Morton
Date: Fri Apr 10 2015 - 17:36:38 EST


On Thu, 9 Apr 2015 01:50:23 +0200 Andi Kleen <andi@xxxxxxxxxxxxxx> wrote:

> > Head is spinning a bit. As this all appears to be shiny new
> > added-by-andi gcc functionality, it would be useful if we could have a
> > few more words describing what it's all about. Reordering of what with
> > respect to what and why and why is it bad. Why is gcc reordering
> > things anyway, and what's the downside of preventing this. Why is the
> > compiler reordering things rather than the linker. etc etc etc.
>
> Ok, let me try.

That was super-useful, thanks. I slurped it into the changelog -
maybe one day it will provide material for Documentation/lto-stuff.txt.

Big picture: do you have a feeling for how much benefit LTO will yield
in the kernel, if/when it's all completed?

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