[Cake] Cake3 - source code and some questions

Stephen Hemminger stephen at networkplumber.org
Wed Apr 22 20:45:25 EDT 2015

On Thu, 23 Apr 2015 00:02:35 +0300
Adrian Popescu <adriannnpopescu at gmail.com> wrote:

> e1000e (82574, dual port and quad port server e1000e adapters with
> various Intel chips) is exhibiting varying latency based on the used
> kernel.
> Local network ping latencies on Ubuntu 14.04 with its LTS 3.13 kernel
> are always below 0.5 milliseconds when idle and lightly loaded. The
> latest kernels from kernel.org are unable to match those latencies.
> These modern kernels are always seeing latencies of 2-3 milliseconds.
> Turning off all offloads on the involved ethernet e1000e network
> interfaces doesn't help. This is all physical Intel hardware with
> e1000e interfaces.
> Two idle hosts on a local network should be able to ping each other
> and get latencies which are always less than one millisecond. FreeBSD
> doesn't have this problem.

These NIC's have had a histrory of power management related issues.
I suspect some power management (maybe even in SMI) is turning off
parts of the chips and it is taking long to turn back on.

More information about the Cake mailing list