linux-kernel - Re: [PATCH 0/5] Add vhost-blk support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20120717132642.GA10590@redhat.com>
Date:	Tue, 17 Jul 2012 16:26:42 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	Stefan Hajnoczi <stefanha@...il.com>, Asias He <asias@...hat.com>,
	linux-kernel@...r.kernel.org, linux-aio@...ck.org,
	kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
	Benjamin LaHaise <bcrl@...ck.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 0/5] Add vhost-blk support

On Tue, Jul 17, 2012 at 03:02:45PM +0200, Paolo Bonzini wrote:
> Il 17/07/2012 14:48, Michael S. Tsirkin ha scritto:
> > On Tue, Jul 17, 2012 at 01:03:39PM +0100, Stefan Hajnoczi wrote:
> >> On Tue, Jul 17, 2012 at 12:54 PM, Michael S. Tsirkin <mst@...hat.com> wrote:
> >>>> Knowing the answer to that is important before anyone can say whether
> >>>> this approach is good or not.
> >>>>
> >>>> Stefan
> >>>
> >>> Why is it?
> >>
> >> Because there might be a fix to kvmtool which closes the gap.  It
> >> would be embarassing if vhost-blk was pushed just because no one
> >> looked into what is actually going on.
> > 
> > Embarrasing to whom? Is someone working on an optimization that
> > makes the work in question redundant, with posting just around
> > the corner? Then maybe the thing to do is just wait a bit.
> 
> Of course there is work going on to make QEMU perform better.
> Not sure about lkvm.
> 
> >> And on the flipside, hard evidence of an overhead that cannot be
> >> resolved could be good reason to do more vhost devices in the future.
> > 
> > How can one have hard evidence of an overhead that cannot be resolved?
> 
> Since we do have two completely independent userspaces (lkvm and
> data-plane QEMU), you can build up some compelling evidence of an
> overhead that cannot be resolved in user space.

OK, so what you are saying benchmark against data-plane QEMU?
I agree actually. Asias, any data?

> >> Either way, it's useful to do this before going further.
> > 
> > I think each work should be discussed on its own merits.  Maybe
> > vhost-blk is just well written. So? What is your conclusion?
> 
> If it's just that vhost-blk is written well, my conclusion is that lkvm
> people should look into improving their virtio-blk userspace.  We take
> hints from each other all the time, for example virtio-scsi will have
> unlocked kick in 3.6.
> 
> Why can't vhost-* just get into staging, and we call it a day?
> 
> Paolo

staging is not a destination. Even if we put a driver in staging it
won't stay there indefinitely if qemu-kvm is not using it,
something that doesn't seem to be addressed for vhost-blk yet.

-- 
MST
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/