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

[Jens Axboe <axboe@kernel.dk>]

On 4/12/22 10:15 AM, Pavel Begunkov wrote:
> On 4/12/22 17:06, Florian Schmaus wrote:
>> 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.

I fixed it up.

-- 
Jens Axboe