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 [thread overview]
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.
>>
>
>
next prev parent 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
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