numa and taskqueues

[Adrian Chadd]

On 30 May 2017 at 07:46, Emeric POUPON <emeric.poupon at stormshield.eu> wrote:
> Hi,
>
>>
>>> 2/ about https://reviews.freebsd.org/D10680, I think it would be great to have
>>> this commited as a first step.
>>> Since it seems to be stuck, maybe I can add more people on this. Any suggestion?
>>
>> Well, what's with the ~ 8% performance decrease? Do you know what's
>> going on? For a "we're parallelising IPSEC operations", seeing it get
>> slower with more flows is a bit concerning.
>>
>> Thanks,
>>
>
> Actually, there is a performance boost only when few flows are involved.
> That's why this is not activated by default and a sysctl is here to enable the feature.
>
> To sum up, the more different flows you process (both ciphered and unciphered), the more network queues are hit and the more CPU units are triggered from ipsec.
> In this case, we indeed notice a loss, certainly due to the extra queing/reordering performed.

Can you dig into that a bit more? Do you know exactly what's going on?
eg, is it a "lock contention" problem? Is it a "stuff is context
switching, thus latency" problem? etc, etc.



-adrian