From mboxrd@z Thu Jan 1 00:00:00 1970 From: robin.murphy@arm.com (Robin Murphy) Date: Tue, 31 May 2016 15:39:06 +0100 Subject: [PATCH v2] arm64: Implement optimised IP checksum helpers In-Reply-To: <574D9E8F.7080509@arm.com> References: <574D9E8F.7080509@arm.com> Message-ID: <574DA20A.4070302@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi James, On 31/05/16 15:24, James Morse wrote: > Hi Robin, > > On 31/05/16 12:22, Robin Murphy wrote: >> AArch64 is capable of 128-bit memory accesses without alignment >> restrictions, which makes it both possible and highly practical to slurp >> up a typical 20-byte IP header in just 2 loads. Implement our own >> version of ip_fast_checksum() to take advantage of that, resulting in >> considerably fewer instructions and memory accesses than the generic >> version. We can also get more optimal code generation for csum_fold() by >> defining it a slightly different way round from the generic version, so >> throw that into the mix too. >> >> Suggested-by: Luke Starrett >> Acked-by: Luke Starrett >> Signed-off-by: Robin Murphy >> --- >> >> Minor changes: include types.h for correctness, add Luke's ack. >> >> arch/arm64/include/asm/checksum.h | 51 +++++++++++++++++++++++++++++++++++++++ > > Maybe a nit, don't you need to remove the 'generic-y += checksum.h' line from > arch/arm64/include/asm/Kbuild to avoid the generated version being created too? [0] I guess you skimmed the very end of the patch ;) +#include > The compiler on my box picks your header in preference to the generated one, but > [1] suggests it isn't to be trusted! We only cherry-pick a couple of functions to optimise, so not building the generic file would necessitate copy-pasting the rest of it. I'd hope this pattern is sufficiently robust, since it's already in use on a number of other architectures! AFAICS [1] only applies when the generic file shouldn't be built at all, so cross fingers we're probably OK. Robin. > Thanks, > > James > > [0] d8ecc5cd8e22 ("kbuild: asm-generic support") > [1] https://lkml.org/lkml/2016/5/23/78 > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel at lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >