Re: [PATCH 5.14 00/12] for-next optimisations

[Pavel Begunkov <asml.silence@gmail.com>]

On 6/14/21 11:37 PM, Pavel Begunkov wrote:
> There are two main lines intervened. The first one is pt.2 of ctx field
> shuffling for better caching. There is a couple of things left on that
> front.
> 
> The second is optimising (assumably) rarely used offset-based timeouts
> and draining. There is a downside (see 12/12), which will be fixed
> later. In plans to queue a task_work clearing drain_used (under
> uring_lock) from io_queue_deferred() once all drainee are gone.

There is a much better way to disable it back: in io_drain_req().
The series is good to go, I'll patch on top later.

> nops(batch=32):
>     15.9 MIOPS vs 17.3 MIOPS
> nullblk (irqmode=2 completion_nsec=0 submit_queues=16), no merges, no stat
>     1002 KIOPS vs 1050 KIOPS
> 
> Though the second test is very slow comparing to what I've seen before,
> so might be not represantative.
> 
> Pavel Begunkov (12):
>   io_uring: keep SQ pointers in a single cacheline
>   io_uring: move ctx->flags from SQ cacheline
>   io_uring: shuffle more fields into SQ ctx section
>   io_uring: refactor io_get_sqe()
>   io_uring: don't cache number of dropped SQEs
>   io_uring: optimise completion timeout flushing
>   io_uring: small io_submit_sqe() optimisation
>   io_uring: clean up check_overflow flag
>   io_uring: wait heads renaming
>   io_uring: move uring_lock location
>   io_uring: refactor io_req_defer()
>   io_uring: optimise non-drain path
> 
>  fs/io_uring.c | 226 +++++++++++++++++++++++++-------------------------
>  1 file changed, 111 insertions(+), 115 deletions(-)
> 

-- 
Pavel Begunkov