powerpc/64s: reduce exception alignment

[Michael Ellerman]

On Thu, 2016-13-10 at 03:43:52 UTC, Nicholas Piggin wrote:
> Exception handlers are aligned to 128 bytes (L1 cache) on 64s, which is
> overkill. It can reduce the icache footprint of any individual exception
> path. However taken as a whole, the expansion in icache footprint seems
> likely to be counter-productive and cause more total misses.
> 
> Create IFETCH_ALIGN_SHIFT/BYTES, which should give optimal ifetch
> alignment with much more reasonable alignment. This saves 1792 bytes
> from head_64.o text with an allmodconfig build.
> 
> Other subarchitectures should define appropriate IFETCH_ALIGN_SHIFT
> values if this becomes more widely used.
> 
> Cc: Anton Blanchard <anton at samba.org>
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/f4329f2ecb149282fdfdd8830a936a

cheers