linux-kernel - RE: [RFC PATCH] virtio-mmio: support for multiple irqs

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Date:	Wed, 5 Nov 2014 08:26:35 +0000
From:	GAUGUEY Rémy 228890 <remy.gauguey@....fr>
To:	Shannon Zhao <zhaoshenglong@...wei.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:	"mst@...hat.com" <mst@...hat.com>,
	"peter.maydell@...aro.org" <peter.maydell@...aro.org>,
	"john.liuli@...wei.com" <john.liuli@...wei.com>,
	"joel.schopp@....com" <joel.schopp@....com>,
	"qemu-devel@...gnu.org" <qemu-devel@...gnu.org>,
	"n.nikolaev@...tualopensystems.com" 
	<n.nikolaev@...tualopensystems.com>,
	"virtualization@...ts.linux-foundation.org" 
	<virtualization@...ts.linux-foundation.org>,
	"peter.huangpeng@...wei.com" <peter.huangpeng@...wei.com>,
	"hangaohuai@...wei.com" <hangaohuai@...wei.com>
Subject: RE: [RFC PATCH] virtio-mmio: support for multiple irqs

Hi Shannon, 

>Type of backend         bandwith(GBytes/sec)
>virtio-net              0.66
>vhost-net               1.49
>vhost-net with irqfd    2.01
>
>Test cmd: ./iperf -c 192.168.0.2 -P 1 -i 10 -p 5001 -f G -t 60

Impressive results !
Could you please detail your setup ? which platform are you using and which GbE controller ?
As a reference, it would be good also to have result with an iperf to the HOST to see how far we are from a native configuration...

Also, I assume a pending Qemu patch is necessary to assign multiple irqs ? I'm correct ? 

Thanks a lot, 
Best regards
Rémy

-----Message d'origine-----
De : Shannon Zhao [mailto:zhaoshenglong@...wei.com] 
Envoyé : mercredi 5 novembre 2014 09:00
À : linux-kernel@...r.kernel.org
Cc : mst@...hat.com; peter.maydell@...aro.org; john.liuli@...wei.com; joel.schopp@....com; GAUGUEY Rémy 228890; qemu-devel@...gnu.org; n.nikolaev@...tualopensystems.com; virtualization@...ts.linux-foundation.org; peter.huangpeng@...wei.com; hangaohuai@...wei.com
Objet : Re: [RFC PATCH] virtio-mmio: support for multiple irqs


On 2014/11/4 17:35, Shannon Zhao wrote:
> As the current virtio-mmio only support single irq, so some advanced 
> features such as vhost-net with irqfd are not supported. And the net 
> performance is not the best without vhost-net and irqfd supporting.
> 
Hi Joel, Peter, Mst,

Some virtio-net with virtio-mmio performance data on ARM added as followed:

Type of backend         bandwith(GBytes/sec)
virtio-net              0.66
vhost-net               1.49
vhost-net with irqfd    2.01

Test cmd: ./iperf -c 192.168.0.2 -P 1 -i 10 -p 5001 -f G -t 60

>From this test data, irqfd has great improvement (about 30%) on performance.
So maybe it's necessary to enable multiple irq support to make vhost-net with virtio-mmio on ARM be able to use irqfd.

How do you guys think? Look forward for your feedback.

Thanks,
Shannon

> This patch support virtio-mmio to request multiple irqs like 
> virtio-pci. With this patch and qemu assigning multiple irqs for 
> virtio-mmio device, it's ok to use vhost-net with irqfd on arm/arm64.
> 
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