linux-kernel - Re: [PATCH 2/2] io_uring: batch getting pcpu references

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Date:   Wed, 18 Dec 2019 13:41:14 +0300
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Jens Axboe <axboe@...nel.dk>, io-uring@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] io_uring: batch getting pcpu references

On 12/18/2019 3:02 AM, Jens Axboe wrote:
> On 12/17/19 3:28 PM, Pavel Begunkov wrote:
>> percpu_ref_tryget() has its own overhead. Instead getting a reference
>> for each request, grab a bunch once per io_submit_sqes().
>>
>> basic benchmark with submit and wait 128 non-linked nops showed ~5%
>> performance gain. (7044 KIOPS vs 7423)
> 
> Confirmed about 5% here as well, doing polled IO to a fast device.
> That's a huge gain!
> 
Great that you got it for a real drive!
As mentioned, after we are done with this one, I have an idea how to
optimise it even further, which would work for small QD as well.

-- 
Pavel Begunkov