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Date:   Tue, 15 Mar 2022 09:55:39 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Kanchan Joshi <joshiiitr@gmail.com>
Cc:     Christoph Hellwig <hch@lst.de>,
        Kanchan Joshi <joshi.k@samsung.com>,
        Jens Axboe <axboe@kernel.dk>, Keith Busch <kbusch@kernel.org>,
        Pavel Begunkov <asml.silence@gmail.com>,
        io-uring@vger.kernel.org, linux-nvme@lists.infradead.org,
        linux-block@vger.kernel.org, sbates@raithlin.com,
        logang@deltatee.com, Pankaj Raghav <pankydev8@gmail.com>,
        Javier =?iso-8859-1?Q?Gonz=E1lez?= <javier@javigon.com>,
        Luis Chamberlain <mcgrof@kernel.org>,
        Adam Manzanares <a.manzanares@samsung.com>,
        Anuj Gupta <anuj20.g@samsung.com>
Subject: Re: [PATCH 08/17] nvme: enable passthrough with fixed-buffer
Message-ID: <20220315085539.GB4132@lst.de>
References: <20220308152105.309618-1-joshi.k@samsung.com> <CGME20220308152709epcas5p1f9d274a0214dc462c22c278a72d8697c@epcas5p1.samsung.com> <20220308152105.309618-9-joshi.k@samsung.com> <20220311064321.GC17232@lst.de> <CA+1E3rKnsdap7wb4RqO7HCBq8hxjF48k9NydMRAKht43xnhB9A@mail.gmail.com>
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On Mon, Mar 14, 2022 at 06:36:17PM +0530, Kanchan Joshi wrote:
> > And I'm also really worried about only supporting fixed buffers.  Fixed
> > buffers are a really nice benchmarketing feature, but without supporting
> > arbitrary buffers this is rather useless in real life.
> 
> Sorry, I did not get your point on arbitrary buffers.
> The goal has been to match/surpass io_uring's block-io peak perf, so
> pre-mapped buffers had to be added.

I'm completely interesting in adding code to the nvme driver that is
just intended for benchmarketing.  The fixed buffers are nice for
benchmarking and a very small number of real use cases (e.g. fixed size
database log), but for this feature to be generally useful for the real
world we'll need to support arbitrary user memory.