Re: [RFC PATCH v3 0/3] Async nvme passthrough over io_uring

From: Kanchan Joshi <joshiiitr@gmail.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: Kanchan Joshi <joshi.k@samsung.com>,
	Christoph Hellwig <hch@lst.de>, Keith Busch <kbusch@kernel.org>,
	 Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>,
	io-uring@vger.kernel.org,  linux-nvme@lists.infradead.org,
	anuj20.g@samsung.com,  Javier Gonzalez <javier.gonz@samsung.com>,
	Nitesh Shetty <nj.shetty@samsung.com>,
	 Selvakumar S <selvakuma.s1@samsung.com>
Subject: Re: [RFC PATCH v3 0/3] Async nvme passthrough over io_uring
Date: Thu, 18 Mar 2021 13:17:52 +0530	[thread overview]
Message-ID: <CA+1E3r+_rNmDBgL2cabxboG4GDaRx=XRt=SiNPt3hnvOuTYd5A@mail.gmail.com> (raw)
In-Reply-To: <63a127c2-e2ed-ad5f-a6d3-8d56e3e95380@kernel.dk>

On Thu, Mar 18, 2021 at 7:28 AM Jens Axboe <axboe@kernel.dk> wrote:
>
> On 3/17/21 3:31 AM, Kanchan Joshi wrote:
> > On Tue, Mar 16, 2021 at 9:31 PM Jens Axboe <axboe@kernel.dk> wrote:
> >>
> >> On 3/16/21 8:01 AM, Kanchan Joshi wrote:
> >>> This series adds async passthrough capability for nvme block-dev over
> >>> iouring_cmd. The patches are on top of Jens uring-cmd branch:
> >>> https://git.kernel.dk/cgit/linux-block/log/?h=io_uring-fops.v3
> >>>
> >>> Application is expected to allocate passthrough command structure, set
> >>> it up traditionally, and pass its address via "block_uring_cmd->addr".
> >>> On completion, CQE is posted with completion-status after any ioctl
> >>> specific buffer/field update.
> >>
> >> Do you have a test app? I'd be curious to try and add support for this
> >> to t/io_uring from fio just to run some perf numbers.
> >
> > Yes Jens. Need to do a couple of things to make it public, will post it today.

Please see if this is accessible to you -
https://github.com/joshkan/fio/commit/6c18653bc87015213a18c23d56518d4daf21b191

I run it on nvme device with the extra option "-uring_cmd=1". And pit
passthru read/write against regular uring read/write.
While write perf looks fine, I notice higher-qd reads going tad-bit
low which is puzzling.
But I need to test more to see if this is about my test-env (including
the added test-code) itself.

It will be great if you could, at some point in future, have a look at
this test or spin off what you already had in mind.

> Sounds good! I commented on 1/3, I think it can be simplified and
> cleaned up quite a bit, which is great. Then let's base it on top of v4
> that I posted, let me know if you run into any issues with that.

Yes, will move to V4,  thanks!

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