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SubjectRe: [PATCH RFC 0/9] nxt propagation + locking optimisation
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On 01/03/2020 19:23, Pavel Begunkov wrote:
> On 01/03/2020 19:18, Pavel Begunkov wrote:
>> There are several independent parts in the patchset, but bundled
>> to make a point.
>> 1-2: random stuff, that implicitly used later.
>> 3-5: restore @nxt propagation
>> 6-8: optimise locking in io_worker_handle_work()
>> 9: optimise io_uring refcounting
>>
>> The next propagation bits are done similarly as it was before, but
>> - nxt stealing is now at top-level, but not hidden in handlers
>> - ensure there is no with REQ_F_DONT_STEAL_NEXT
>>
>> [6-8] is the reason to dismiss the previous @nxt propagation appoach,
>> I didn't found a good way to do the same. Even though it looked
>> clearer and without new flag.
>>
>> Performance tested it with link-of-nops + IOSQE_ASYNC:
>>
>> link size: 100
>> orig: 501 (ns per nop)
>> 0-8: 446
>> 0-9: 416
>>
>> link size: 10
>> orig: 826
>> 0-8: 776
>> 0-9: 756
>
> BTW, that's basically QD1, and with contention for wqe->lock the gap should be
> even wider.

And another notice: "orig" actually includes [1-5], so @nxt propagation was
working there.

>>
>> Pavel Begunkov (9):
>> io_uring: clean up io_close
>> io-wq: fix IO_WQ_WORK_NO_CANCEL cancellation
>> io_uring: make submission ref putting consistent
>> io_uring: remove @nxt from handlers
>> io_uring: get next req on subm ref drop
>> io-wq: shuffle io_worker_handle_work() code
>> io-wq: io_worker_handle_work() optimise locking
>> io-wq: optimise double lock for io_get_next_work()
>> io_uring: pass submission ref to async
>>
>> fs/io-wq.c | 162 ++++++++++++----------
>> fs/io_uring.c | 366 ++++++++++++++++++++++----------------------------
>> 2 files changed, 258 insertions(+), 270 deletions(-)
>>
>

--
Pavel Begunkov

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