DPDK patches and discussions
 help / color / mirror / Atom feed
From: Jason Wang <jasowang@redhat.com>
To: Alejandro Lucero <alejandro.lucero@netronome.com>,
	"Michael S. Tsirkin" <mst@redhat.com>
Cc: Thomas Monjalon <thomas.monjalon@6wind.com>, dev <dev@dpdk.org>,
	"Xie, Huawei" <huawei.xie@intel.com>,
	<yuanhan.liu@linux.intel.com>
Subject: Re: [dpdk-dev] [PATCH 2/2] virtio: support IOMMU platform
Date: Mon, 5 Sep 2016 00:31:52 -0600	[thread overview]
Message-ID: <bc9d4282-e668-0d42-c1e0-989a54adf4eb@redhat.com> (raw)
Message-ID: <20160905063152.G9CnCyxFBkgEuy4PhpgmlKNo3pC5VFv0rTcxldcP9hI@z> (raw)
In-Reply-To: <CAD+H991ohd4N_NAyL-pMgo8PkHbWXj67CitHGCXX3J=_1113Ng@mail.gmail.com>



On 2016年09月04日 16:08, Alejandro Lucero wrote:
> I know RedHat is working on a vIOMMU so I guess this work is related 
> to that effort, but it is a surprise virtio using IOMMU. I thought 
> IOMMU just made sense when using SRIOV. My second guess is using IOMMU 
> with virtio is a matter of security, but by other hand, virtio + IOMMU 
> could imply serious performance degradation when multiple VMs are in use.

We will use qemu vIOMMU for virito, so there's no such issue.

> I'm talking about IOMMU contention, exactly about IOTLB contention.

I thought device IOTLB (ATS) was just designed to solve this contention.

> This performance issue is complex to describe or even analyze as there 
> are several factors having an impact on it. For example, 1GB hugepages 
> can avoid most of it and the same if TX & RX rings are not bigger than 
> 256. So, my question: is RedHat aware of this potential IOMMU 
> contention which can limit scalability?

For virtio, we use vIOMMU per VM and implement a device IOTLB in vhost 
side. Technically, it does not have such issue I think.

Thanks

>
> On Fri, Sep 2, 2016 at 6:26 PM, Michael S. Tsirkin <mst@redhat.com 
> <mailto:mst@redhat.com>> wrote:
>
>     On Fri, Sep 02, 2016 at 03:04:56PM +0200, Thomas Monjalon wrote:
>     > 2016-09-02 14:37, Jason Wang:
>     > > Virtio pmd doesn't support VFIO in the past since devices
>     bypass IOMMU
>     > > completely. But recently, the work of making virtio device
>     work with
>     > > IOMMU is near to complete.
>     >
>     > Good news!
>     > What are the requirements for Qemu and Linux version numbers please?
>
>     I expect QEMU 2.8 and Linux 4.8 to have the support.
>
>

  reply	other threads:[~2016-09-08  4:18 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-02  6:36 [dpdk-dev] [PATCH 1/2] net/virtio: support modern device id Jason Wang
2016-09-02  6:37 ` [dpdk-dev] [PATCH 2/2] virtio: support IOMMU platform Jason Wang
2016-09-02 13:04   ` Thomas Monjalon
2016-09-02 17:26     ` Michael S. Tsirkin
2016-09-04  8:08       ` Alejandro Lucero
2016-09-05  6:31         ` Jason Wang [this message]
2016-09-05  6:31           ` Jason Wang
2016-09-05  6:31           ` Jason Wang
2016-09-05  5:15     ` Jason Wang
2016-09-05  6:25     ` Jason Wang
2016-09-05  6:25       ` Jason Wang
2016-09-05  6:25       ` Jason Wang
     [not found]   ` <20160905071626.GM30752@yliu-dev.sh.intel.com>
2016-09-06  7:46     ` Yuanhan Liu
2016-09-07  4:53       ` Jason Wang
2016-09-02 12:57 ` [dpdk-dev] [PATCH 1/2] net/virtio: support modern device id Thomas Monjalon
2016-09-05  6:36   ` Jason Wang
2016-09-05  6:36     ` Jason Wang
2016-09-05  6:36     ` Jason Wang

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=bc9d4282-e668-0d42-c1e0-989a54adf4eb@redhat.com \
    --to=jasowang@redhat.com \
    --cc=alejandro.lucero@netronome.com \
    --cc=dev@dpdk.org \
    --cc=huawei.xie@intel.com \
    --cc=mst@redhat.com \
    --cc=thomas.monjalon@6wind.com \
    --cc=yuanhan.liu@linux.intel.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).