Re: [PATCH 9/9] io_uring: optimise io_get_cqe()

[Florian Schmaus <flo@geekplace.eu>]

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On 12/04/2022 16.09, Pavel Begunkov wrote:
> io_get_cqe() is expensive because of a bunch of loads, masking, etc.
> However, most of the time we should have enough of entries in the CQ,
> so we can cache two pointers representing a range of contiguous CQE
> memory we can use. When the range is exhausted we'll go through a slower
> path to set up a new range. When there are no CQEs avaliable, pointers
> will naturally point to the same address.
> 
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
> ---
>   fs/io_uring.c | 46 +++++++++++++++++++++++++++++++++++-----------
>   1 file changed, 35 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index b349a3c52354..f2269ffe09eb 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -416,6 +416,13 @@ struct io_ring_ctx {
>   	unsigned long		check_cq_overflow;
>   
>   	struct {
> +		/*
> +		 * We cache a range of free CQEs we can use, once exhausted it
> +		 * should go through a slower range setup, see __io_get_cqe()
> +		 */
> +		struct io_uring_cqe	*cqe_cached;
> +		struct io_uring_cqe	*cqe_santinel;

I think this should s/santinel/sentinel.

- Flow

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