[vfio-users] RLIMIT_MEMLOCK exceeded when enabling intremap

[Alex Williamson]

On Wed, 4 Jul 2018 16:05:08 +0530
Prasun Ratn <prasun.ratn at gmail.com> wrote:

> Thanks Alex - that was all very helpful!
> 
> I am still a bit new to this, so that was very informative. I am
> trying to add multiple NVMe drives to a VM and I misunderstood this
> intremap setting. I just need to make sure that the *host* has
> intremap=on . Is there any qemu config needed to get the best perf out
> of the VMs? Do Posted Interrupts get enabled by default?

Host interrupt remapping should be on by default, you can tell by
seeing "IR" prefixed on all the interrupt types in /proc/interrupts.
There are *lots* of configuration parameters needed to get the best
performance from a VM, this is no small topic.  From hugepages to vCPU
type and topology, to NUMA locality, to paravirtualized drivers and
guest enlightenments, to CPU isolation and IRQ balancing.  Please do
some research, there's lots of information on these topics and
generally there is not a one-size-fits-all solution, you need to
evaluate the trade-offs in some cases whether you're tuning for absolute
VM performance or simply a well tuned VM on a general purpose host.
Posted interrupts are enabled by default if the host supports it.
Thanks,

Alex