Re: [LKP] Re: [io_uring] 584b0180f0: phoronix-test-suite.fio.SequentialWrite.IO_uring.Yes.Yes.1MB.DefaultTestDirectory.mb_s -10.2% regression

[Jens Axboe]

On 7/19/22 2:58 AM, Yin Fengwei wrote:
> Hi Jens,
> 
> On 7/19/2022 10:29 AM, Jens Axboe wrote:
>> I'll poke at this tomorrow.
> 
> Just FYI. Another finding (test is based on commit 584b0180f0):
> If the code block is put to different function, the fio performance result is
> different:

I think this turned out to be a little bit of a goose chase. What's
happening here is that later kernels defer the file assignment, which
means it isn't set if a request is queued with IOSQE_ASYNC. That in
turn, for writes, means that we don't hash it on io-wq insertion, and
then it doesn't get serialized with other writes to that file.

I'll come up with a patch for this that you can test.

-- 
Jens Axboe