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SubjectRe: [PATCH] net: improve ipv4 performances
On Sun,  1 Apr 2018 20:31:21 +0200
Anton Gary Ceph <agaceph@gmail.com> wrote:

> As the Linux networking stack is growing, more and more protocols are
> added, increasing the complexity of stack itself.
> Modern processors, contrary to common belief, are very bad in branch
> prediction, so it's our task to give hints to the compiler when possible.
>
> After a few profiling and analysis, turned out that the ethertype field
> of the packets has the following distribution:
>
> 92.1% ETH_P_IP
> 3.2% ETH_P_ARP
> 2.7% ETH_P_8021Q
> 1.4% ETH_P_PPP_SES
> 0.6% don't know/no opinion
>
> From a projection on statistics collected by Google about IPv6 adoption[1],
> IPv6 should peak at 25% usage at the beginning of 2030. Hence, we should
> give proper hints to the compiler about the low IPv6 usage.
>
> Here is an iperf3 run before and after the patch:
>
> Before:
> [ ID] Interval Transfer Bandwidth Retr
> [ 4] 0.00-100.00 sec 100 GBytes 8.60 Gbits/sec 0 sender
> [ 4] 0.00-100.00 sec 100 GBytes 8.60 Gbits/sec receiver
>
> After
> [ ID] Interval Transfer Bandwidth Retr
> [ 4] 0.00-100.00 sec 109 GBytes 9.35 Gbits/sec 0 sender
> [ 4] 0.00-100.00 sec 109 GBytes 9.35 Gbits/sec receiver
>
> [1] https://www.google.com/intl/en/ipv6/statistics.html
>
> Signed-off-by: Anton Gary Ceph <agaceph@gmail.com>

I am surprised it makes that much of an impact.

It would be easier to manage future bisection if the big patch
was split into several pieces. Bridge, bonding, netfilter, etc.
There doesn't appear to be any direct cross dependencies.


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