IOMMU

IOMMU (Input–Output Memory Management) Settings

Some hardware, including the Mellanox/Nvidia 100G NICs, support IOMMU. While IOMMU is particularly important in a virtualized environment, we've seen parallel stream throughput go from 80 Gbps to 180 Gbps on non-virtualized hosts as well. We recommend enabling this for any host with a NIC 100 Gbps or higher.

iommu support must be configured in grub.

Add this line to the file: /etc/default/grub

   GRUB_CMDLINE_LINUX="iommu=pt" 

You might also want to try these settings:

   GRUB_CMDLINE_LINUX="intel_iommu=on iommu=pt" 

or

   GRUB_CMDLINE_LINUX="amd_iommu=on iommu=pt" 

Depending on your host architecture.

Then do:

  /usr/sbin/update-grub

and reboot.

To confirm the setting worked, do: 

   cat \/proc\/cmdline

and you should see something like:

  root=/dev/mapper/vg0-root ro iommu=pt

For more information, see:

• Linux Kernel Command Line Parameters
• Nvidia support article