can the scheduler decide to schedule an interrupted but runnable thread on another CPU core? What are the implications for code?

[Adrian Chadd]

On 14 February 2014 08:39, John Baldwin <jhb at freebsd.org> wrote:
> On Friday, February 14, 2014 4:22:34 am Adrian Chadd wrote:
>> Ok, so now I remember the other odd thing.
>>
>> I was seeing the sending context(s) jumping from one CPU to another
>> during flowtable_insert_common(), around the locking bits.
>>
>> But I thread pinned all the sender user threads!
>>
>> So, why would the senders still be scheduled on other CPUs if I've
>> pinned the userland threads?
>>
>> (and yes, I verified that the userland threads weren't moving around.)
>
> Can you clarify a bit?  It's not clear how sender thraeds differ from
> userland threads differ from sender user threads.  (I.e. one reading
> is that these are all the same thing and should thus all be pinned
> (I assume you mean using cpuset to bind them to specific cores rather
> than sched_pin))

Yup, I'm doing a manual, poor-mans RSS in lieu of merging in roberts stuff:

* the userland threads are using the cpuset call to map a thread into
a cpuset, yes
* the NIC TX/RX ring routines in cxgbe are pinned to the same CPU as
the userland threads


-a