Re: [GIT PULL] x86/misc for 6.5

[Arjan van de Ven]

On 6/27/2023 3:43 PM, Linus Torvalds wrote:
> On Tue, 27 Jun 2023 at 15:25, Linus Torvalds
> <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> > I don't know what the rules are - and some of the functions you test
> > seem actively buggy (ie not handling alignment right etc).
>
> Oh. And you *only* test the 40-byte case. That seems a bit bogus.
>
> If I change the packet size from 40 to 1500, I get
>
>    02: 185.1 / 186.4 cycles (8b414316) Upcoming linux kernel version
>    04: 184.9 / 186.5 cycles (8b414316) Specialized to size 40
>    06: 107.3 / 117.2 cycles (8b414316) New version
>    22: 185.6 / 186.5 cycles (8b414316) Odd-alignment handling removed
>
> which seems unexpectedly bad for the other versions.

I'm not surprised though; running 2 parallel streams (where one stream has a fixed zero as input,
so can run OOO any time) .. can really have a performance change like this