On Wed, Mar 22, 2017 at 09:43:04PM +0800, Aaron Lu wrote: > On Wed, Mar 22, 2017 at 05:55:12PM +0900, Minchan Kim wrote: > > On Wed, Mar 22, 2017 at 04:41:04PM +0800, Aaron Lu wrote: > > > My understanding of the unbound workqueue is that it will create a > > > thread pool for each node, versus each CPU as in the bound workqueue > > > case, and use threads from the thread pool(create threads if not enough) > > > to do the work. > > > > Yes, that was my understand so I read code and found that > > > > insert_work: > > .. > > if (__need_more_worker(pool)) > > wake_up_worker(pool); > > > > so I thought if there is a running thread in that node, workqueue > > will not wake any other threads so parallelism should be max 2. > > AFAIK, if the work goes sleep, scheduler will spawn new worker > > thread so the active worker could be a lot but I cannot see any > > significant sleepable point in that work(ie, batch_free_work). > > Looks like worker_thread() will spawn new worker through manage_worker(). > > Note that pool->nr_running will always be zero for an unbound workqueue > and thus need_more_worker() will return true as long as there are queued > work items in the pool.
Aha, it solves my wonder. Thanks a lot!
