Re: [PATCH 2/9] IB: add a proper completion queue abstraction

From: Christoph Hellwig
Date: Fri Nov 20 2015 - 05:16:52 EST

On Wed, Nov 18, 2015 at 10:20:14AM -0800, Bart Van Assche wrote:
> Are you perhaps referring to the sysfs CPU mask that allows to control
> workqueue affinity ?

I think he is referring to the defintion of WQ_UNBOUND:


Work items queued to an unbound wq are served by the special
woker-pools which host workers which are not bound to any
specific CPU. This makes the wq behave as a simple execution
context provider without concurrency management. The unbound
worker-pools try to start execution of work items as soon as
possible. Unbound wq sacrifices locality but is useful for
the following cases.

* Wide fluctuation in the concurrency level requirement is
expected and using bound wq may end up creating large number
of mostly unused workers across different CPUs as the issuer
hops through different CPUs.

* Long running CPU intensive workloads which can be better
managed by the system scheduler.

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