linux-kernel - Re: [PATCH 0/3] zone-append support in aio and io-uring

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Date:   Thu, 18 Jun 2020 10:46:48 +0200
From:   Matias Bjørling <mb@...htnvm.io>
To:     Javier González <javier@...igon.com>
Cc:     Kanchan Joshi <joshi.k@...sung.com>, axboe@...nel.dk,
        viro@...iv.linux.org.uk, bcrl@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-aio@...ck.org, io-uring@...r.kernel.org,
        linux-block@...r.kernel.org, selvakuma.s1@...sung.com,
        nj.shetty@...sung.com, Damien Le Moal <Damien.LeMoal@....com>,
        Keith Busch <keith.busch@....com>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH 0/3] zone-append support in aio and io-uring

On 18/06/2020 10.39, Javier González wrote:
> On 18.06.2020 10:32, Matias Bjørling wrote:
>> On 18/06/2020 10.27, Javier González wrote:
>>> On 18.06.2020 10:04, Matias Bjørling wrote:
>>>> On 17/06/2020 19.23, Kanchan Joshi wrote:
>>>>> This patchset enables issuing zone-append using aio and io-uring 
>>>>> direct-io interface.
>>>>>
>>>>> For aio, this introduces opcode IOCB_CMD_ZONE_APPEND. Application 
>>>>> uses start LBA
>>>>> of the zone to issue append. On completion 'res2' field is used to 
>>>>> return
>>>>> zone-relative offset.
>>>>>
>>>>> For io-uring, this introduces three opcodes: 
>>>>> IORING_OP_ZONE_APPEND/APPENDV/APPENDV_FIXED.
>>>>> Since io_uring does not have aio-like res2, cqe->flags are 
>>>>> repurposed to return zone-relative offset
>>>>
>>>> Please provide a pointers to applications that are updated and 
>>>> ready to take advantage of zone append.
>>>
>>> Good point. We are posting a RFC with fio support for append. We wanted
>>> to start the conversation here before.
>>>
>>> We can post a fork for improve the reviews in V2.
>>
>> Christoph's response points that it is not exactly clear how this 
>> matches with the POSIX API.
>
> Yes. We will address this.
>>
>> fio support is great - but I was thinking along the lines of 
>> applications that not only benchmark performance. fio should be part 
>> of the supported applications, but should not be the sole reason the 
>> API is added.
>
> Agree. It is a process with different steps. We definitely want to have
> the right kernel interface before pushing any changes to libraries and /
> or applications. These will come as the interface becomes more stable.
>
> To start with xNVMe will be leveraging this new path. A number of
> customers are leveraging the xNVMe API for their applications already.

Heh, let me be even more specific - open-source applications, that is 
outside of fio (or any other benchmarking application), and libraries 
that acts as a mediator between two APIs.