[Oisf-users] Question about cpu-affinity

[Eric Leblond]

Hi Cooper,

On Thu, 2018-03-01 at 08:12 -0800, Cooper F. Nelson wrote:
> Hi Eric,
> 
> I hope you don't mind me copying you directly, as I saw you were the
> author of the threading/cpu-affinity module.

That was long ago ;)

> I'm wondering if it is currently possible when using multiple
> interfaces
> to 'interleave' the threads so that they are evenly distributed
> across
> all cores.  For example, consider a system with 16 cores and two
> interfaces, configured with 8 threads each.
> 
> Can you do something like this?
> 
>   - detect-cpu-set
> 
>         cpu: [ 0, 2, 4, 6, 8, 10, 12, 14, 1, 3, 5, 7, 9, 11, 13, 15 ]
> 
>         mode: "exclusive"
> 
> The idea is we want the first 8 threads allocated to 0-14, even cores
> only.  The next 8 threads being allocated to 1-16, odd cores only. 
> Lets
> assume we are using RSS in this example.
> 
> I had a look at the code and while it appears that this how you have
> implemented it, I'm not 100% certain, so I wanted to verify.

I don't think this will work. The CPU set is an unordered. Suricata
build the CPU set as a map then it start by 0, get next CPU in the set
(testing if 0 is in then switching to 1 and checking if it is in the
set).

So with current code, the only way to do what you want is to have a
["all"] CPU set in exclusive mode in the affinity and an ugly af-packet 
configuration like:

  af-packet:
    - interface: eth0
      threads: 1
      cluster-id: 99
    - interface: eth1
      threads: 1
      cluster-id: 98
    - interface: eth0
      threads: 1
      cluster-id: 99
    - interface: eth1
      threads: 1
      cluster-id: 98
    ...
    -
default:
      #set every global variable here


BR,
-- 
Eric Leblond <eric at regit.org>