Messages in this thread | | | Subject | Re: workqueue: Only kick a worker after thawed or for an unbound workqueue | From | Yunfeng Ye <> | Date | Wed, 18 Nov 2020 14:26:49 +0800 |
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On 2020/11/18 12:06, Lai Jiangshan wrote: > On Tue, Nov 17, 2020 at 3:33 PM Yunfeng Ye <yeyunfeng@huawei.com> wrote: >> >> In realtime scenario, We do not want to have interference on the >> isolated cpu cores. but when invoking alloc_workqueue() for percpu wq >> on the housekeeping cpu, it kick a kworker on the isolated cpu. >> >> alloc_workqueue >> pwq_adjust_max_active >> wake_up_worker >> >> The comment in pwq_adjust_max_active() said: >> "Need to kick a worker after thawed or an unbound wq's >> max_active is bumped" >> >> So it is unnecessary to kick a kworker for percpu wq's when >> alloc_workqueue. this patch only kick a worker after thawed or for an >> unbound workqueue. >> >> Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com> >> --- >> kernel/workqueue.c | 18 +++++++++++++----- >> 1 file changed, 13 insertions(+), 5 deletions(-) >> >> diff --git a/kernel/workqueue.c b/kernel/workqueue.c >> index c41c3c17b86a..80f7bbd4889f 100644 >> --- a/kernel/workqueue.c >> +++ b/kernel/workqueue.c >> @@ -3696,14 +3696,16 @@ static void pwq_unbound_release_workfn(struct work_struct *work) >> } >> >> /** >> - * pwq_adjust_max_active - update a pwq's max_active to the current setting >> + * pwq_adjust_max_active_and_kick - update a pwq's max_active to the current setting >> * @pwq: target pool_workqueue >> + * @force_kick: force to kick a worker >> * >> * If @pwq isn't freezing, set @pwq->max_active to the associated >> * workqueue's saved_max_active and activate delayed work items >> * accordingly. If @pwq is freezing, clear @pwq->max_active to zero. >> */ >> -static void pwq_adjust_max_active(struct pool_workqueue *pwq) >> +static void pwq_adjust_max_active_and_kick(struct pool_workqueue *pwq, >> + bool force_kick) >> { >> struct workqueue_struct *wq = pwq->wq; >> bool freezable = wq->flags & WQ_FREEZABLE; >> @@ -3733,9 +3735,10 @@ static void pwq_adjust_max_active(struct pool_workqueue *pwq) >> >> /* >> * Need to kick a worker after thawed or an unbound wq's >> - * max_active is bumped. It's a slow path. Do it always. >> + * max_active is bumped. > > > Hello > > Thanks for reporting the problem. > > But I don't like to add an argument. The waking up is called > always just because it was considered no harm and it is slow > path. But it can still be possible to detect if the waking up > is really needed based on the actual activation of delayed works. > > The previous lines are: > > while (!list_empty(&pwq->delayed_works) && > pwq->nr_active < pwq->max_active) > pwq_activate_first_delayed(pwq); > > And you can record the old pwq->nr_active before these lines: > > int old_nr_active = pwq->nr_active; > > while (!list_empty(&pwq->delayed_works) && > pwq->nr_active < pwq->max_active) > pwq_activate_first_delayed(pwq); > > /* please add more comments here, see 951a078a5 */ > if (old_nr_active < pwq->nr_active) { > if (!old_nr_active || (wq->flags & WQ_UNBOUND)) > wake_up_worker(pwq->pool); > } > Ok, I will send a patch v2. Thanks.
> > Thanks for your work. > Lai. > >> */ >> - wake_up_worker(pwq->pool); >> + if (force_kick || (wq->flags & WQ_UNBOUND)) >> + wake_up_worker(pwq->pool); >> } else { >> pwq->max_active = 0; >> } >> @@ -3743,6 +3746,11 @@ static void pwq_adjust_max_active(struct pool_workqueue *pwq) >> raw_spin_unlock_irqrestore(&pwq->pool->lock, flags); >> } >> >> +static void pwq_adjust_max_active(struct pool_workqueue *pwq) >> +{ >> + pwq_adjust_max_active_and_kick(pwq, false); >> +} >> + >> /* initialize newly alloced @pwq which is associated with @wq and @pool */ >> static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq, >> struct worker_pool *pool) >> @@ -5252,7 +5260,7 @@ void thaw_workqueues(void) >> list_for_each_entry(wq, &workqueues, list) { >> mutex_lock(&wq->mutex); >> for_each_pwq(pwq, wq) >> - pwq_adjust_max_active(pwq); >> + pwq_adjust_max_active_and_kick(pwq, true); >> mutex_unlock(&wq->mutex); >> } >> >> -- >> 2.18.4 > . >
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