Messages in this thread | | | Subject | Re: [RFC PATCH v4 01/13] ktask: add documentation | From | Randy Dunlap <> | Date | Mon, 5 Nov 2018 13:19:50 -0800 |
| |
On 11/5/18 8:55 AM, Daniel Jordan wrote: > Motivates and explains the ktask API for kernel clients. > > Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com> > --- > Documentation/core-api/index.rst | 1 + > Documentation/core-api/ktask.rst | 213 +++++++++++++++++++++++++++++++ > 2 files changed, 214 insertions(+) > create mode 100644 Documentation/core-api/ktask.rst
Hi,
> diff --git a/Documentation/core-api/ktask.rst b/Documentation/core-api/ktask.rst > new file mode 100644 > index 000000000000..c3c00e1f802f > --- /dev/null > +++ b/Documentation/core-api/ktask.rst > @@ -0,0 +1,213 @@ > +.. SPDX-License-Identifier: GPL-2.0+ > + > +============================================ > +ktask: parallelize CPU-intensive kernel work > +============================================ > + > +:Date: November, 2018 > +:Author: Daniel Jordan <daniel.m.jordan@oracle.com> > + > + > +Introduction > +============
[snip]
> +Resource Limits > +=============== > + > +ktask has resource limits on the number of work items it sends to workqueue.
to a workqueue. or: to workqueues.
> +In ktask, a workqueue item is a thread that runs chunks of the task until the > +task is finished. > + > +These limits support the different ways ktask uses workqueues: > + - ktask_run to run threads on the calling thread's node. > + - ktask_run_numa to run threads on the node(s) specified. > + - ktask_run_numa with nid=NUMA_NO_NODE to run threads on any node in the > + system. > + > +To support these different ways of queueing work while maintaining an efficient > +concurrency level, we need both system-wide and per-node limits on the number
I would prefer to refer to ktask as ktask instead of "we", so s/we need/ktask needs/
> +of threads. Without per-node limits, a node might become oversubscribed > +despite ktask staying within the system-wide limit, and without a system-wide > +limit, we can't properly account for work that can run on any node.
s/we/ktask/
> + > +The system-wide limit is based on the total number of CPUs, and the per-node > +limit on the CPU count for each node. A per-node work item counts against the > +system-wide limit. Workqueue's max_active can't accommodate both types of > +limit, no matter how many workqueues are used, so ktask implements its own. > + > +If a per-node limit is reached, the work item is allowed to run anywhere on the > +machine to avoid overwhelming the node. If the global limit is also reached, > +ktask won't queue additional work items until we fall below the limit again.
s/we fall/ktask falls/ or s/we fall/it falls/
> + > +These limits apply only to workqueue items--that is, helper threads beyond the > +one starting the task. That way, one thread per task is always allowed to run.
thanks. -- ~Randy
| |