Messages in this thread | | | Subject | Re: [PATCH -next RFC v2 8/8] sbitmap: wake up the number of threads based on required tags | From | "yukuai (C)" <> | Date | Sat, 9 Apr 2022 10:17:37 +0800 |
| |
在 2022/04/09 5:13, Bart Van Assche 写道: > On 4/8/22 00:39, Yu Kuai wrote: >> +static unsigned int get_wake_nr(struct sbq_wait_state *ws, unsigned >> int nr_tags) >> +{ >> + struct sbq_wait *wait; >> + struct wait_queue_entry *entry; >> + unsigned int nr = 1; >> + >> + spin_lock_irq(&ws->wait.lock); >> + list_for_each_entry(entry, &ws->wait.head, entry) { >> + wait = container_of(entry, struct sbq_wait, wait); >> + if (nr_tags <= wait->nr_tags) >> + break; >> + >> + nr++; >> + nr_tags -= wait->nr_tags; >> + } >> + spin_unlock_irq(&ws->wait.lock); >> + >> + return nr; >> +} >> + >> static bool __sbq_wake_up(struct sbitmap_queue *sbq) >> { >> struct sbq_wait_state *ws; >> @@ -648,7 +668,7 @@ static bool __sbq_wake_up(struct sbitmap_queue *sbq) >> smp_mb__before_atomic(); >> atomic_set(&ws->wait_cnt, wake_batch); >> sbq_update_preemption(sbq, wake_batch); >> - wake_up_nr(&ws->wait, wake_batch); >> + wake_up_nr(&ws->wait, get_wake_nr(ws, wake_batch)); >> return true; >> } > > An additional comment: my understanding is that __sbq_wake_up() should > wake up exactly `wake_batch` waiters. The above patch changes that into > waking up at most `wake_batch` waiters. I think that's wrong. Hi,
I think the reason to wake up 'wake_batch' waiters is to make sure wakers will use up 'wake_batch' tags that is just freed, because each wakers should aquire at least one tag. Thus I think if we can make sure wakers will use up 'wake_batch' tags, it's ok to wake up less waiters.
Please kindly correct me if I'm wrong.
Thanks, Kuai > > Bart. > . >
| |