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

From: Long Li <longli@microsoft.com>
To: vkuznets <vkuznets@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Bart Van Assche <bvanassche@acm.org>,
	"longli@linuxonhyperv.com" <longli@linuxonhyperv.com>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
	Jonathan Corbet <corbet@lwn.net>,
	KY Srinivasan <kys@microsoft.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Hans de Goede <hdegoede@redhat.com>,
	"Williams, Dan J" <dan.j.williams@intel.com>,
	Maximilian Luz <luzmaximilian@gmail.com>,
	Mike Rapoport <rppt@kernel.org>,
	Ben Widawsky <ben.widawsky@intel.com>,
	Jiri Slaby <jirislaby@kernel.org>,
	Andra Paraschiv <andraprs@amazon.com>,
	Siddharth Gupta <sidgup@codeaurora.org>,
	Hannes Reinecke <hare@suse.de>
Subject: RE: [Patch v5 0/3] Introduce a driver to support host accelerated access to Microsoft Azure Blob for Azure VM
Date: Mon, 11 Oct 2021 17:57:04 +0000	[thread overview]
Message-ID: <BY5PR21MB15065897C3D2461637986D60CEB59@BY5PR21MB1506.namprd21.prod.outlook.com> (raw)
In-Reply-To: <87a6jj3asl.fsf@vitty.brq.redhat.com>

> 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@linuxfoundation.org> writes:
> 
> > On Fri, Oct 08, 2021 at 01:11:02PM +0200, Vitaly Kuznetsov wrote:
> >> Greg Kroah-Hartman <gregkh@linuxfoundation.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.

Thank you for this great suggestion. I'm preparing some diagrams for describing the problem. I will be sending them soon.

Thanks,

Long

> 
> --
> Vitaly