Re: [dpdk-users] Dpdk poor performance on virtual machine

[Jes Nielsen <jes.nielsen@6wind.com>]

Are you perhaps running on an old Sandy Bridge x86?

I heard that Intel Sandy Bridge CPUs have a limitation with their VT-d
IOTLB that limits PCIe passthrough throughput. Sandy Bridge (and earlier)
CPUs are not recommended if high performance is required.

On Thu, Dec 15, 2016 at 1:14 PM, Stephen Hemminger <
stephen@networkplumber.org> wrote:

> On Thu, 15 Dec 2016 19:29:54 +0200
> edgar helmut <helmut.edgar100@gmail.com> wrote:
>
> > Stephen, this is not the case, it relies on using the transparent
> hugepages
> > which looks like 2M hugepages size.
> > Why should be a problem to back 1G pages of the guest to 2M pages at the
> > host?
> > the transparent hugepages makes the deployment much more flexible.
>
>
> The IOMMU has a cache (like TLB) which has a limited number of slots.
> If using 2M pages then the IOMMU cache misses will cause a performance drop
> just like CPU cache misses.  I think Intel had some slides back at IDF 2012
> that showed the impact.
>
>


-- 

Best Regards,

Jes Nielsen

6WIND, Solutions Engineering
Austin, TX 78730, USA
Tel: (512) 426-8222

www.6wind.com

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