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From: Jens Axboe <[email protected]>
To: Pavel Begunkov <[email protected]>, [email protected]
Subject: Re: [PATCH for-next v2 11/12] io_uring: do msg_ring in target task via tw
Date: Wed, 7 Dec 2022 14:22:26 -0700	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 12/7/22 2:18 PM, Pavel Begunkov wrote:
> On 12/7/22 15:51, Jens Axboe wrote:
>> On 12/7/22 8:31 AM, Jens Axboe wrote:
>>> On 12/6/22 8:53?PM, Pavel Begunkov wrote:
>>>> @@ -43,6 +61,15 @@ static int io_msg_ring_data(struct io_kiocb *req)
>>>>       if (msg->src_fd || msg->dst_fd || msg->flags)
>>>>           return -EINVAL;
>>>>   +    if (target_ctx->task_complete && current != target_ctx->submitter_task) {
>>>> +        init_task_work(&msg->tw, io_msg_tw_complete);
>>>> +        if (task_work_add(target_ctx->submitter_task, &msg->tw,
>>>> +                  TWA_SIGNAL))
>>>> +            return -EOWNERDEAD;
>>>> +
>>>> +        return IOU_ISSUE_SKIP_COMPLETE;
>>>> +    }
>>>> +
>>>
>>> We should probably be able to get by with TWA_SIGNAL_NO_IPI here, no?
>>
>> Considering we didn't even wake before, I'd say that's a solid yes.
> 
> I'm not so sure. It'll work, but a naive approach would also lack
> IORING_SETUP_TASKRUN_FLAG and so mess with latencies when it's not
> desirable.
> 
> option 1)
> 
> method = TWA_SIGNAL;
> if (flags & IORING_SETUP_TASKRUN_FLAG)
>     method = NO_IPI;
> 
> option 2)
> 
> task_work_add(NO_IPI);
> atomic_or(IORING_SQ_TASKRUN, &ctx->rings->sq_flags);
> 
> 
> Might be better to have one of those.

I like option 2, which should be fine.

-- 
Jens Axboe



  reply	other threads:[~2022-12-07 21:22 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-07  3:53 [PATCH for-next v2 00/12] CQ locking optimisation Pavel Begunkov
2022-12-07  3:53 ` [PATCH for-next v2 01/12] io_uring: dont remove file from msg_ring reqs Pavel Begunkov
2022-12-07 13:52   ` Jens Axboe
2022-12-07 21:12     ` Pavel Begunkov
2022-12-07 21:23       ` Jens Axboe
2022-12-07  3:53 ` [PATCH for-next v2 02/12] io_uring: improve io_double_lock_ctx fail handling Pavel Begunkov
2022-12-07  3:53 ` [PATCH for-next v2 03/12] io_uring: skip overflow CQE posting for dying ring Pavel Begunkov
2022-12-07  3:53 ` [PATCH for-next v2 04/12] io_uring: don't check overflow flush failures Pavel Begunkov
2022-12-07  3:53 ` [PATCH for-next v2 05/12] io_uring: complete all requests in task context Pavel Begunkov
2022-12-07  3:53 ` [PATCH for-next v2 06/12] io_uring: force multishot CQEs into " Pavel Begunkov
2022-12-07  3:53 ` [PATCH for-next v2 07/12] io_uring: use tw for putting rsrc Pavel Begunkov
2022-12-07  3:53 ` [PATCH for-next v2 08/12] io_uring: never run tw and fallback in parallel Pavel Begunkov
2022-12-07  3:53 ` [PATCH for-next v2 09/12] io_uring: get rid of double locking Pavel Begunkov
2022-12-07  3:53 ` [PATCH for-next v2 10/12] io_uring: extract a io_msg_install_complete helper Pavel Begunkov
2022-12-07  3:53 ` [PATCH for-next v2 11/12] io_uring: do msg_ring in target task via tw Pavel Begunkov
2022-12-07 15:31   ` Jens Axboe
2022-12-07 15:51     ` Jens Axboe
2022-12-07 21:18       ` Pavel Begunkov
2022-12-07 21:22         ` Jens Axboe [this message]
2022-12-07  3:53 ` [PATCH for-next v2 12/12] io_uring: skip spinlocking for ->task_complete Pavel Begunkov

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