linux-kernel - Re: [dm-devel] [PATCH v1 0/5] dm: dm-user: New target that proxies BIOs to userspace

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Message-ID: <CAGF4SLgDvS7VOih4XZ+sqx6jVK3wBQZan+uZMVsdYdVEPZdrpw@mail.gmail.com>
Date:   Wed, 16 Dec 2020 13:24:59 -0500
From:   Vitaly Mayatskih <v.mayatskih@...il.com>
To:     Palmer Dabbelt <palmer@...belt.com>
Cc:     josef@...icpanda.com, bvanassche@....org,
        Christoph Hellwig <hch@...radead.org>,
        Mike Snitzer <snitzer@...hat.com>, corbet@....net,
        kernel-team@...roid.com, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org,
        Song Liu <song@...nel.org>, dm-devel@...hat.com,
        linux-kselftest@...r.kernel.org, shuah@...nel.org, agk@...hat.com,
        michael.christie@...cle.com
Subject: Re: [dm-devel] [PATCH v1 0/5] dm: dm-user: New target that proxies
 BIOs to userspace

On Mon, Dec 14, 2020 at 10:03 PM Palmer Dabbelt <palmer@...belt.com> wrote:

> I was really experting someone to say that.  It does seem kind of silly to build
> out the new interface, but not go all the way to a ring buffer.  We just didn't
> really have any way to justify the extra complexity as our use cases aren't
> that high performance.   I kind of like to have benchmarks for this sort of
> thing, though, and I didn't have anyone who had bothered avoiding the last copy
> to compare against.

I worked on something very similar, though performance was one of the
goals. The implementation was floating around lockless ring buffers,
shared memory for zerocopy, multiqueue and error handling. It could be
that every disk storage vendor has to implement something like that in
order to bridge Linux kernel to their own proprietary datapath running
in userspace.

-- 
wbr, Vitaly