# Re: \[PATCH\] x86/lib: Remove the special case for odd-aligned buffers in csum\_partial.c

- From: Dave Hansen \<hidden\>
- Date: 2021-12-13 15:02:51 
- List: netdev
- Page: https://ratatoskr.run/netdev/2021/12/1606834
- Thread: https://ratatoskr.run/netdev/2021/12/1606819/t.md

```text
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 <redacted>
> ---
> 
> 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*?
```