netdev - Re: provide vhost thread per virtqueue for forwarding scenario

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Date:	Mon, 20 May 2013 11:16:03 +0300
From:	Abel Gordon <ABELG@...ibm.com>
To:	Qinchuanyu <qinchuanyu@...wei.com>
Cc:	kvm-owner@...r.kernel.org,
	"nab@...ux-iscsi.org" <nab@...ux-iscsi.org>,
	" (netdev@...r.kernel.org)" <netdev@...r.kernel.org>,
	"rusty@...tcorp.com.au" <rusty@...tcorp.com.au>,
	Zanghongyong <zanghongyong@...wei.com>,
	"Zhangjie (HZ)" <zhang.zhangjie@...wei.com>, nyharel@...il.com,
	"Muli Ben-Yehuda" <mulix@...ix.org>, orit.was@...il.com,
	"Michael S. Tsirkin" <mst@...hat.com>
Subject: Re: provide vhost thread per virtqueue for forwarding scenario



"Michael S. Tsirkin" <mst@...hat.com> wrote on 20/05/2013 10:43:00 AM:

> >
> > I did the test with kernel 3.0.27 and qemu-1.4.0, guest is suse11-
> sp2, and then two vhost thread provide
> > double tx/rx forwarding performance than signal vhost thread.
> > The virtqueue of vhost_blk is 1, so it still use one vhost thread
> without change.
> >
> > Is there something wrong in this solution? If not, I would list patch
later.
> >
> > Best regards
> > King
>
> Yes, I don't think we want to create threads even more aggressively
> in all cases. I'm worried about scalability as it is.
> I think we should explore a flexible approach, use a thread pool
> (for example, a wq) to share threads between virtqueues,
> switch to a separate thread only if there's free CPU and existing
> threads are busy. Hopefully share threads between vhost instances too.
>

Qinchuanyu, you can take a look at the following tech. report
http://domino.research.ibm.com/library/cyberdig.nsf/1e4115aea78b6e7c85256b360066f0d4/479e3578ed05bfac85257b4200427735!OpenDocument


which actually shows the scalability problem Michael mentioned when
you run multiple vhost-threads.

Regards,
Abel.


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