Re: [RFC] gcc feature request: Moving blocks into sections

From: Mathieu Desnoyers
Date: Tue Aug 06 2013 - 16:33:28 EST

* Steven Rostedt (rostedt@xxxxxxxxxxx) wrote:
> On Tue, 2013-08-06 at 10:48 -0700, Linus Torvalds wrote:
> > So I wonder if this is a "ok, let's not bother, it's not worth the
> > pain" issue. 128 bytes of offset is very small, so there probably
> > aren't all that many cases that would use it.
> OK, I'll forward port the original patches for the hell of it anyway,
> and post it as an RFC. Let people play with it if they want, and if it
> seems like it would benefit the kernel perhaps we can reconsider.
> It shouldn't be too hard to do the forward port, and if we don't ever
> take it, it would be a fun exercise regardless ;-)
> Actually, the first three patches should be added as they are clean ups
> and safety checks. Nothing to do with the actual 2-5 byte jumps. They
> were lost due to their association with the complex patches. :-/

Steve, perhaps you could add a mode to your binary rewriting program
that counts the number of 2-byte vs 5-byte jumps found, and if possible
get a breakdown of those per subsystem ? It might help us getting a
clearer picture of how many important sites, insn cache-wise, are being
shrinked by this approach.



> -- Steve

Mathieu Desnoyers
EfficiOS Inc.
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