On Fri, Jul 18, 2014 at 06:05:14PM -0400, Tejun Heo wrote: > On Wed, Jul 16, 2014 at 06:09:58PM +0800, Lai Jiangshan wrote: > > In this code: > > if ((worker->flags & WORKER_UNBOUND) && need_more_worker(pool)) > > wake_up_worker(pool); > > > > the first test is unneeded. Even the first test is removed, it doesn't > > affect > > the wake-up logic when WORKER_UNBOUND. And it will not introduce any useless > > wake-up when !WORKER_UNBOUND since the nr_running >= 1 except only one case. > > It will introduce useless/redundant wake-up when cpu_intensive, but this > > case is rare and next patch will also remove this redundant wake-up. > > > > Signed-off-by: Lai Jiangshan <la...@cn.fujitsu.com> > > --- > > kernel/workqueue.c | 7 ++----- > > 1 files changed, 2 insertions(+), 5 deletions(-) > > > > diff --git a/kernel/workqueue.c b/kernel/workqueue.c > > index f8d54c1..6d11b9a 100644 > > --- a/kernel/workqueue.c > > +++ b/kernel/workqueue.c > > @@ -2047,11 +2047,8 @@ __acquires(&pool->lock) > > if (unlikely(cpu_intensive)) > > worker_set_flags(worker, WORKER_CPU_INTENSIVE, true); > > > > - /* > > - * Unbound pool isn't concurrency managed and work items should be > > - * executed ASAP. Wake up another worker if necessary. > > - */ > > - if ((worker->flags & WORKER_UNBOUND) && need_more_worker(pool)) > > + /* Wake up another worker if necessary. */ > > + if (need_more_worker(pool)) > > wake_up_worker(pool); > > What does this buy us? Sure, it may achieve about the same operation > but it's a lot more confusing. need_more_worker() is specifically for > concurrency management. Applying it to unmanaged workers could lead > to okay behavior but conflating the two to save one test on worker > flags doesn't seem like a good trade-off to me.
I take this back. We do guarantee that need_more_worker() returns %true for unbound pools and make use of that fact but I'd like it to retain the comment about unbound pools. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
