linux-kernel - Re: [Patch v5 0/3] Introduce a driver to support host accelerated access to Microsoft Azure Blob for Azure VM

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Message-ID: <87a6jj3asl.fsf@vitty.brq.redhat.com>
Date:   Fri, 08 Oct 2021 15:28:58 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Long Li <longli@...rosoft.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bart Van Assche <bvanassche@....org>,
        "longli@...uxonhyperv.com" <longli@...uxonhyperv.com>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Hans de Goede <hdegoede@...hat.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        Maximilian Luz <luzmaximilian@...il.com>,
        Mike Rapoport <rppt@...nel.org>,
        Ben Widawsky <ben.widawsky@...el.com>,
        Jiri Slaby <jirislaby@...nel.org>,
        Andra Paraschiv <andraprs@...zon.com>,
        Siddharth Gupta <sidgup@...eaurora.org>,
        Hannes Reinecke <hare@...e.de>
Subject: Re: [Patch v5 0/3] Introduce a driver to support host accelerated
 access to Microsoft Azure Blob for Azure VM

Greg Kroah-Hartman <gregkh@...uxfoundation.org> writes:

> On Fri, Oct 08, 2021 at 01:11:02PM +0200, Vitaly Kuznetsov wrote:
>> Greg Kroah-Hartman <gregkh@...uxfoundation.org> writes:
>> 
>> ...
>> >
>> > Not to mention the whole crazy idea of "let's implement our REST api
>> > that used to go over a network connection over an ioctl instead!"
>> > That's the main problem that you need to push back on here.
>> >
>> > What is forcing you to put all of this into the kernel in the first
>> > place?  What's wrong with the userspace network connection/protocol that
>> > you have today?
>> >
>> > Does this mean that we now have to implement all REST apis that people
>> > dream up as ioctl interfaces over a hyperv transport?  That would be
>> > insane.
>> 
>> As far as I understand, the purpose of the driver is to replace a "slow"
>> network connection to API endpoint with a "fast" transport over
>> Vmbus.
>
> Given that the network connection is already over vmbus, how is this
> "slow" today?  I have yet to see any benchmark numbers anywhere :(
>
>> So what if instead of implementing this new driver we just use
>> Hyper-V Vsock and move API endpoint to the host?
>
> What is running on the host in the hypervisor that is supposed to be
> handling these requests?  Isn't that really on some other guest?
>

Long,

would it be possible to draw a simple picture for us describing the
backend flow of the feature, both with network connection and with this
new driver? We're struggling to understand which particular bottleneck
the driver is trying to eliminate.

-- 
Vitaly