Messages in this thread | | | Subject | Re: [PATCH] x86/lib: Remove the special case for odd-aligned buffers in csum_partial.c | From | Dave Hansen <> | Date | Mon, 13 Dec 2021 07:02:24 -0800 |
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On 12/13/21 6:43 AM, David Laight wrote: > There is no need to special case the very unusual odd-aligned buffers. > They are no worse than 4n+2 aligned buffers. > > Signed-off-by: David Laight <david.laight@aculab.com> > --- > > On an i7-7700 misaligned buffers add 2 or 3 clocks (in 115) to a 512 byte > checksum. > That is just measuring the main loop with an lfence prior to rdpmc to > read PERF_COUNT_HW_CPU_CYCLES.
I'm a bit confused by this changelog.
Are you saying that the patch causes a (small) performance regression?
Are you also saying that the optimization here is not worth it because it saves 15 lines of code? Or that the misalignment checks themselves add 2 or 3 cycles, and this is an *optimization*?
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