On 11/4/21 5:35 AM, Hao Xu wrote:
> 在 2021/11/4 上午3:10, Jens Axboe 写道:
>> On 10/31/21 4:49 AM, Hao Xu wrote:
>>> @@ -380,10 +382,14 @@ static void io_wqe_dec_running(struct io_worker *worker)
>>> if (!(worker->flags & IO_WORKER_F_UP))
>>> return;
>>>
>>> + raw_spin_lock(&acct->lock);
>>> if (atomic_dec_and_test(&acct->nr_running) && io_acct_run_queue(acct)) {
>>> + raw_spin_unlock(&acct->lock);
>>> atomic_inc(&acct->nr_running);
>>> atomic_inc(&wqe->wq->worker_refs);
>>> io_queue_worker_create(worker, acct, create_worker_cb);
>>> + } else {
>>> + raw_spin_unlock(&acct->lock);
>>> }
>>> }
>>
>> I think this may be more readable as:
>>
>> static void io_wqe_dec_running(struct io_worker *worker)
>> __must_hold(wqe->lock)
>> {
>> struct io_wqe_acct *acct = io_wqe_get_acct(worker);
>> struct io_wqe *wqe = worker->wqe;
>>
>> if (!(worker->flags & IO_WORKER_F_UP))
>> return;
>> if (!atomic_dec_and_test(&acct->nr_running))
>> return;
>>
>> raw_spin_lock(&acct->lock);
>> if (!io_acct_run_queue(acct)) {
>> raw_spin_unlock(&acct->lock);
>> return;
>> }
>>
>> raw_spin_unlock(&acct->lock);
>> atomic_inc(&acct->nr_running);
>> atomic_inc(&wqe->wq->worker_refs);
>> io_queue_worker_create(worker, acct, create_worker_cb);
>> }
>>
>> ?
>>
>> Patch looks pretty sane to me, but there's a lot of lock shuffling going
>> on for it. Like in io_worker_handle_work(), and particularly in
>> io_worker_handle_work(). I think it'd be worthwhile to spend some time
>> to see if that could be improved. These days, lock contention is more
>> about frequency of lock grabbing rather than hold time. Maybe clean
>> nesting of wqe->lock -> acct->lock (which would be natural) can help
>> that?
> Sure, I'm working on reduce the lock contension further, will
> update it and send the whole patchset later.
Sounds good, thanks!
--
Jens Axboe
