Messages in this thread | | | From | Noah Goldstein <> | Date | Thu, 25 Nov 2021 00:47:46 -0600 | Subject | Re: [tip:x86/core 1/1] arch/x86/um/../lib/csum-partial_64.c:98:12: error: implicit declaration of function 'load_unaligned_zeropad' |
| |
On Thu, Nov 25, 2021 at 12:32 AM Eric Dumazet <edumazet@google.com> wrote: > > On Wed, Nov 24, 2021 at 9:09 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote: > > > > > > > > Although I see slightly worse performance with aligned `buff` in > > the branch-free approach. Imagine if non-aligned `buff` is that > > uncommon might be better to speculate past the work of `ror`. > > Yes, no clear win here removing the conditional (same cost really), > although using a ror32() is removing the from32to16() helper and get > rid of one folding. > > I will formally submit this change, thanks !
Great :)
Can you put me on the cc list? I have a patch for the function that I'll post once yours gets through.
> > diff --git a/arch/x86/lib/csum-partial_64.c b/arch/x86/lib/csum-partial_64.c > index 1eb8f2d11f7c785be624eba315fe9ca7989fd56d..cf4bd3ef66e56c681b3435d43011ece78438376d > 100644 > --- a/arch/x86/lib/csum-partial_64.c > +++ b/arch/x86/lib/csum-partial_64.c > @@ -11,16 +11,6 @@ > #include <asm/checksum.h> > #include <asm/word-at-a-time.h> > > -static inline unsigned short from32to16(unsigned a) > -{ > - unsigned short b = a >> 16; > - asm("addw %w2,%w0\n\t" > - "adcw $0,%w0\n" > - : "=r" (b) > - : "0" (b), "r" (a)); > - return b; > -} > - > /* > * Do a checksum on an arbitrary memory area. > * Returns a 32bit checksum. > @@ -41,6 +31,7 @@ __wsum csum_partial(const void *buff, int len, __wsum sum) > if (unlikely(odd)) { > if (unlikely(len == 0)) > return sum; > + temp64 = ror32((__force u32)sum, 8); > temp64 += (*(unsigned char *)buff << 8); > len--; > buff++; > @@ -129,10 +120,8 @@ __wsum csum_partial(const void *buff, int len, __wsum sum) > #endif > } > result = add32_with_carry(temp64 >> 32, temp64 & 0xffffffff); > - if (unlikely(odd)) { > - result = from32to16(result); > - result = ((result >> 8) & 0xff) | ((result & 0xff) << 8); > - } > + if (unlikely(odd)) > + result = ror32(result, 8); > return (__force __wsum)result; > } > EXPORT_SYMBOL(csum_partial);
| |