From mboxrd@z Thu Jan 1 00:00:00 1970 From: robin.murphy@arm.com (Robin Murphy) Date: Tue, 31 May 2016 15:43:39 +0100 Subject: [PATCH v2] arm64: Implement optimised IP checksum helpers In-Reply-To: <574DA20A.4070302@arm.com> References: <574D9E8F.7080509@arm.com> <574DA20A.4070302@arm.com> Message-ID: <574DA31B.3080309@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 31/05/16 15:39, Robin Murphy wrote: > 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 Oh wait, I'm being a massive idiot - include/asm-generic is not the same thing as arch/arm/include/generated/asm, is it? I see what you mean now, and yes it probably does want fixing... Sorry! Robin. >> 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 >> > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel at lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel