Benjamin Herrenschmidt <b...@kernel.crashing.org> wrote on 14/01/2010 09:57:11: > Subject: Re: [PATCH]: powerpc: Fix build breakage due to incorrect location > ofautoconf.h > > > > Seen it now as it is in Linus tree: > > > > 1) IMHO it would have been nicer to use #ifdef __KERNEL__ > > instead of CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS > > as then arches that don't define CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS > > at all will never use the new optimization or was that what you intended? > > No, that was on purpose. If an arch doesn't have efficient unaligned > accesses, then they should not use the optimization since it will result > in a lot of unaligned accesses :-) In which case they are better off > falling back to the old byte-by-byte method.
Not quite, it is only 1 of 4 accesses that uses unaligned and that accesses is only unaligned 50% in average, it might still be faster. We will never know now. > > The advantage also of doing it this way is that x86 will benefit from > the optimisation at boot time since it does include autoconf.h in its But so does my suggestion, doesn't it? > boot wrapper (and deals with unaligned accesses just fine at any time) > though something tells me that it won't make much of a difference in > performances on any recent x86 (it might on some of the newer low power > embedded ones, I don't know for sure). _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
