lkml.org 
[lkml]   [2023]   [Jun]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [GIT PULL] x86/misc for 6.5
From
On 6/27/2023 4:02 PM, Linus Torvalds wrote:
> On Tue, 27 Jun 2023 at 15:51, Arjan van de Ven <arjan@linux.intel.com> wrote:
>>
>> 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
>
> How much do people care?
>
> One of the advantages of just having that single "update_csum_40b()"
> function is that it's trivial to then manually unroll.
>
> With a 4-way unrolling, I get
>
> 02: 184.0 / 184.5 cycles (8b414316) Upcoming linux kernel version
> 04: 184.0 / 184.2 cycles (8b414316) Specialized to size 40
> 06: 89.4 / 102.5 cycles (512daed6) New version
> 22: 184.6 / 184.4 cycles (8b414316) Odd-alignment handling removed
>
> but doesn't most network hardware do the csum on its own anyway? How
> critical is csum_partial(), really?

the hardware does most cases..
in
https://lore.kernel.org/netdev/20211111181025.2139131-1-eric.dumazet@gmail.com/
Eric kind of implies it's for IPv6 headers in practice


\
 
 \ /
  Last update: 2023-06-28 01:06    [W:0.058 / U:0.172 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site