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 < [email protected]> wrote: > On Thu, 15 Dec 2016 19:29:54 +0200 > edgar helmut <[email protected]> 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 This e-mail message, including any attachments, is for the sole use of the intended recipient(s) and contains information that is confidential and proprietary to 6WIND. All unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies of the original message.
