Messages in this thread | | | Subject | Re: [RFC][PATCH 3/2] x86/jump labels: Count and display the short jumps used | From | "H. Peter Anvin" <> | Date | Wed, 07 Aug 2013 12:27:51 -0700 |
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Well we do... both to extract relocations and to sort the exception table. Perhaps we need to merge those kinds of postprocessing tools?
Linus Torvalds <torvalds@linux-foundation.org> wrote: >On Wed, Aug 7, 2013 at 10:54 AM, Steven Rostedt <rostedt@goodmis.org> >wrote: >> >> On another box, using a distro config, I had even better results: >> >> [ 2.352448] short jumps: 193 >> [ 2.355407] long jumps: 219 > >.. well, another way of looking at this is to say that all of this >effort saves just 579 bytes. > >Yes, maybe some of those bytes are in really hot paths, but the other >side of *that* coin is that the 2-vs-5 byte jump doesn't much matter >if it's already cached. > >So I'd vote for not doing this. If we had some simple way to do the >short jumps, I think it would be lovely. Or if we had to parse the ELF >files and do instruction rewriting for various other reasons, and the >jump rewriting was just one small detail. > >But using 576 new lines (the diffstat for your patch 1/2 that adds the >infrastructure to do the rewriting) in order to same just about >exactly that many bytes in the binary - the effort just doesn't work >out, imnsho. > > Linus
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