linux-kernel - Re: [PATCH v3 0/6] add persistent submission state

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Date:   Sat, 1 Feb 2020 03:31:21 +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 v3 0/6] add persistent submission state

On 01/02/2020 01:32, Pavel Begunkov wrote:
> On 01/02/2020 01:22, Jens Axboe wrote:
>> On 1/31/20 3:15 PM, Pavel Begunkov wrote:
>>> Apart from unrelated first patch, this persues two goals:
>>>
>>> 1. start preparing io_uring to move resources handling into
>>> opcode specific functions
>>>
>>> 2. make the first step towards long-standing optimisation ideas
>>>
>>> Basically, it makes struct io_submit_state embedded into ctx, so
>>> easily accessible and persistent, and then plays a bit around that.
>>
>> Do you have any perf/latency numbers for this? Just curious if we
>> see any improvements on that front, cross submit persistence of
>> alloc caches should be a nice sync win, for example, or even
>> for peak iops by not having to replenish the pool for each batch.
>>
>> I can try and run some here too.
>>
> 
> I tested the first version, but my drive is too slow, so it was only nops and
> hence no offloading. Honestly, there waren't statistically significant results.
> I'll rerun anyway.
> 
> I have a plan to reuse it for a tricky optimisation, but thinking twice, I can
> just stash it until everything is done. That's not the first thing in TODO and
> will take a while.
> 

I've got numbers, but there is nothing really interesting. Throughput is
insignificantly better with the patches, but I'd need much more experiments
across reboots to confirm that.

Let's postpone the patchset for later

-- 
Pavel Begunkov



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