Messages in this thread | | | Date | Tue, 13 Nov 2018 08:34:00 -0800 | From | Tejun Heo <> | Subject | Re: [RFC PATCH v4 05/13] workqueue, ktask: renice helper threads to prevent starvation |
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Hello, Daniel.
On Mon, Nov 05, 2018 at 11:55:50AM -0500, Daniel Jordan wrote: > static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr, > - bool from_cancel) > + struct nice_work *nice_work, int flags) > { > struct worker *worker = NULL; > struct worker_pool *pool; > @@ -2868,11 +2926,19 @@ static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr, > if (pwq) { > if (unlikely(pwq->pool != pool)) > goto already_gone; > + > + /* not yet started, insert linked work before work */ > + if (unlikely(flags & WORK_FLUSH_AT_NICE)) > + insert_nice_work(pwq, nice_work, work);
So, I'm not sure this works that well. e.g. what if the work item is waiting for other work items which are at lower priority? Also, in this case, it'd be a lot simpler to simply dequeue the work item and execute it synchronously.
> } else { > worker = find_worker_executing_work(pool, work); > if (!worker) > goto already_gone; > pwq = worker->current_pwq; > + if (unlikely(flags & WORK_FLUSH_AT_NICE)) { > + set_user_nice(worker->task, nice_work->nice); > + worker->flags |= WORKER_NICED; > + } > }
I'm not sure about this. Can you see whether canceling & executing synchronously is enough to address the latency regression?
Thanks.
-- tejun
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