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From: Jens Axboe <[email protected]>
To: Pavel Begunkov <[email protected]>, [email protected]
Subject: Re: [PATCH 17/17] io_uring: defer flushing cached reqs
Date: Tue, 9 Feb 2021 19:10:58 -0700	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <e9ba205c3894e88cfbca879b386bbce19c34d150.1612915326.git.asml.silence@gmail.com>

On 2/9/21 5:03 PM, Pavel Begunkov wrote:
> Awhile there are requests in the allocation cache -- use them, only if
> those ended go for the stashed memory in comp.free_list. As list
> manipulation are generally heavy and are not good for caches, flush them
> all or as much as can in one go.
> 
> Signed-off-by: Pavel Begunkov <[email protected]>
> ---
>  fs/io_uring.c | 29 +++++++++++++++++++----------
>  1 file changed, 19 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index 64d3f3e2e93d..17194e0d62ff 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -1953,25 +1953,34 @@ static inline void io_req_complete(struct io_kiocb *req, long res)
>  	__io_req_complete(req, 0, res, 0);
>  }
>  
> +static void io_flush_cached_reqs(struct io_submit_state *state)
> +{
> +	do {
> +		struct io_kiocb *req = list_first_entry(&state->comp.free_list,
> +						struct io_kiocb, compl.list);
> +
> +		list_del(&req->compl.list);
> +		state->reqs[state->free_reqs++] = req;
> +		if (state->free_reqs == ARRAY_SIZE(state->reqs))
> +			break;
> +	} while (!list_empty(&state->comp.free_list));
> +}
> +
>  static struct io_kiocb *io_alloc_req(struct io_ring_ctx *ctx)
>  {
>  	struct io_submit_state *state = &ctx->submit_state;
>  
>  	BUILD_BUG_ON(IO_REQ_ALLOC_BATCH > ARRAY_SIZE(state->reqs));
>  
> -	if (!list_empty(&state->comp.free_list)) {
> -		struct io_kiocb *req;
> -
> -		req = list_first_entry(&state->comp.free_list, struct io_kiocb,
> -					compl.list);
> -		list_del(&req->compl.list);
> -		return req;
> -	}
> -
>  	if (!state->free_reqs) {
>  		gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
>  		int ret;
>  
> +		if (!list_empty(&state->comp.free_list)) {
> +			io_flush_cached_reqs(state);
> +			goto out;
> +		}

I think that'd be cleaner as:

	if (io_flush_cached_reqs(state))
		goto got_req;

and have io_flush_cached_reqs() return true/false depending on what it did.

-- 
Jens Axboe


  reply	other threads:[~2021-02-10  2:13 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-10  0:03 [PATCH RFC 00/17] playing around req alloc Pavel Begunkov
2021-02-10  0:03 ` [PATCH 01/17] io_uring: replace force_nonblock with flags Pavel Begunkov
2021-02-10  0:03 ` [PATCH 02/17] io_uring: make op handlers always take issue flags Pavel Begunkov
2021-02-10  0:03 ` [PATCH 03/17] io_uring: don't propagate io_comp_state Pavel Begunkov
2021-02-10 14:00   ` Pavel Begunkov
2021-02-10 14:27     ` Jens Axboe
2021-02-10  0:03 ` [PATCH 04/17] io_uring: don't keep submit_state on stack Pavel Begunkov
2021-02-10  0:03 ` [PATCH 05/17] io_uring: remove ctx from comp_state Pavel Begunkov
2021-02-10  0:03 ` [PATCH 06/17] io_uring: don't reinit submit state every time Pavel Begunkov
2021-02-10  0:03 ` [PATCH 07/17] io_uring: replace list with array for compl batch Pavel Begunkov
2021-02-10  0:03 ` [PATCH 08/17] io_uring: submit-completion free batching Pavel Begunkov
2021-02-10  0:03 ` [PATCH 09/17] io_uring: remove fallback_req Pavel Begunkov
2021-02-10  0:03 ` [PATCH 10/17] io_uring: count ctx refs separately from reqs Pavel Begunkov
2021-02-10  0:03 ` [PATCH 11/17] io_uring: persistent req cache Pavel Begunkov
2021-02-10  0:03 ` [PATCH 12/17] io_uring: feed reqs back into alloc cache Pavel Begunkov
2021-02-10  0:03 ` [PATCH 13/17] io_uring: use persistent request cache Pavel Begunkov
2021-02-10  2:14   ` Jens Axboe
2021-02-10  0:03 ` [PATCH 14/17] io_uring: provide FIFO ordering for task_work Pavel Begunkov
2021-02-10  0:03 ` [PATCH 15/17] io_uring: enable req cache for task_work items Pavel Begunkov
2021-02-10  0:03 ` [PATCH 16/17] io_uring: take comp_state from ctx Pavel Begunkov
2021-02-10  0:03 ` [PATCH 17/17] io_uring: defer flushing cached reqs Pavel Begunkov
2021-02-10  2:10   ` Jens Axboe [this message]
2021-02-10  2:08 ` [PATCH RFC 00/17] playing around req alloc Jens Axboe
2021-02-10  3:14   ` Pavel Begunkov
2021-02-10  3:23     ` Jens Axboe
2021-02-10 11:53       ` Pavel Begunkov
2021-02-10 14:27         ` Jens Axboe

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