DPDK patches and discussions
 help / color / mirror / Atom feed
From: Shivapriya  Hiremath <shivpri.b@gmail.com>
To: Alex Markuze <alex@weka.io>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] Why do we need iommu=pt?
Date: Tue, 21 Oct 2014 09:53:44 -0700
Message-ID: <CAKU5Fo-djWmG46gCYUScqOwJzDFoAwPvJvUrBdwss+D=nHLVqA@mail.gmail.com> (raw)
In-Reply-To: <CAKfHP0U-v2fLQwyEa3KBZs3kXpVMQdLU+WgLzQq6xxmrb3Brtg@mail.gmail.com>

Hi,

Thank you for all the replies.
I am trying to understand the impact of this on DPDK. What will be the
repercussions of disabling "iommu=pt" on the DPDK performance?


On Tue, Oct 21, 2014 at 12:32 AM, Alex Markuze <alex@weka.io> wrote:

> DPDK uses a 1:1 mapping and doesn't support IOMMU.  IOMMU allows for
> simpler VM physical address translation.
> The second role of IOMMU is to allow protection from unwanted memory
> access by an unsafe devise that has DMA privileges. Unfortunately this
> protection comes with an extremely high performance costs for high speed
> nics.
>
> To your question iommu=pt disables IOMMU support for the hypervisor.
>
> On Tue, Oct 21, 2014 at 1:39 AM, Xie, Huawei <huawei.xie@intel.com> wrote:
>
>>
>>
>> > -----Original Message-----
>> > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Shivapriya
>> Hiremath
>> > Sent: Monday, October 20, 2014 2:59 PM
>> > To: dev@dpdk.org
>> > Subject: [dpdk-dev] Why do we need iommu=pt?
>> >
>> > Hi,
>> >
>> > My question is that if the Poll mode  driver used the DMA kernel
>> interface
>> > to set up its mappings appropriately, would it still require that
>> iommu=pt
>> > be set?
>> > What is the purpose of setting iommu=pt ?
>> PMD allocates memory though hugetlb file system, and fills the physical
>> address
>> into the descriptor.
>> pt is used to pass through iotlb translation. Refer to the below link.
>> http://lkml.iu.edu/hypermail/linux/kernel/0906.2/02129.html
>> >
>> > Thank you.
>>
>
>

  reply	other threads:[~2014-10-21 16:45 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-10-20 21:58 Shivapriya Hiremath
2014-10-20 22:39 ` Xie, Huawei
2014-10-21  7:32   ` Alex Markuze
2014-10-21 16:53     ` Shivapriya Hiremath [this message]
2014-10-21 19:10       ` Zhou, Danny
2014-10-22  7:35         ` alex
2014-10-22  8:53           ` Liang, Cunming
2014-10-22 15:21             ` Zhou, Danny
2014-10-23  7:49               ` Alex Markuze
2014-10-27 17:27               ` Shivapriya Hiremath
2014-10-27 17:32                 ` Zhou, Danny
2014-10-30 23:22                 ` Zhou, Danny
2014-10-31  0:05                   ` Shivapriya Hiremath

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='CAKU5Fo-djWmG46gCYUScqOwJzDFoAwPvJvUrBdwss+D=nHLVqA@mail.gmail.com' \
    --to=shivpri.b@gmail.com \
    --cc=alex@weka.io \
    --cc=dev@dpdk.org \
    /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

DPDK patches and discussions

This inbox may be cloned and mirrored by anyone:

	git clone --mirror https://inbox.dpdk.org/dev/0 dev/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 dev dev/ https://inbox.dpdk.org/dev \
		dev@dpdk.org
	public-inbox-index dev

Example config snippet for mirrors.
Newsgroup available over NNTP:
	nntp://inbox.dpdk.org/inbox.dpdk.dev


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git