Re: [RFC 0/4] completion locking optimisation feature

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

On 3/18/22 13:52, Pavel Begunkov wrote:
> A WIP feature optimising out CQEs posting spinlocking for some use cases.
> For a more detailed description see 4/4.
> 
> Quick benchmarking with fio/t/io_uring nops gives extra 4% to throughput for
> QD=1, and ~+2.5% for QD=4.

Non-io_uring overhead (syscalls + userspace) takes ~60% of all execution
time, so the percentage should quite depend on the CPU and the kernel config.
Likely to be more than 4% for a faster setup.

fwiw, was also usingIORING_ENTER_REGISTERED_RING, if it's not yet included
in the upstream version of the tool.

Also, want to play after to see if we can also avoid taking uring_lock.


> Pavel Begunkov (4):
>    io_uring: get rid of raw fill cqe in kill_timeout
>    io_uring: get rid of raw fill_cqe in io_fail_links
>    io_uring: remove raw fill_cqe from linked timeout
>    io_uring: optimise compl locking for non-shared rings
> 
>   fs/io_uring.c                 | 126 ++++++++++++++++++++++------------
>   include/uapi/linux/io_uring.h |   1 +
>   2 files changed, 85 insertions(+), 42 deletions(-)
> 

-- 
Pavel Begunkov