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

From: "Matias Bjørling" <mb@lightnvm.io>
To: "Javier González" <javier@javigon.com>
Cc: Kanchan Joshi <joshi.k@samsung.com>,
	axboe@kernel.dk, viro@zeniv.linux.org.uk, bcrl@kvack.org,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-aio@kvack.org, io-uring@vger.kernel.org,
	linux-block@vger.kernel.org, selvakuma.s1@samsung.com,
	nj.shetty@samsung.com, Damien Le Moal <Damien.LeMoal@wdc.com>,
	Keith Busch <keith.busch@wdc.com>, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 0/3] zone-append support in aio and io-uring
Date: Thu, 18 Jun 2020 10:46:48 +0200	[thread overview]
Message-ID: <01581df5-d1d0-2375-23b2-20fc34dcdefd@lightnvm.io> (raw)
In-Reply-To: <20200618083940.jzjtbfwwyyyhpnhs@mpHalley.local>

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.