On Tue, Mar 30, 2010 at 04:48:25PM -0700, Sridhar Samudrala wrote:
> This patch increases the current hardcoded limit of NR_IOBUS_DEVS
> from 6 to 200. We are hitting this limit when creating a guest with more
> than 1 virtio-net device using vhost-net backend. Each virtio-net
> device requires 2 such devices to service notifications from rx/tx queues.
>
> Signed-off-by: Sridhar Samudrala <s...@us.ibm.com>
>
I tried this, but observed a measurable performance
degradation with vhost net and this patch. Did not
investigate yet. Do you see this as well?
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index a3fd0f9..7fb48d3 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -54,7 +54,7 @@ extern struct kmem_cache *kvm_vcpu_cache;
> */
> struct kvm_io_bus {
> int dev_count;
> -#define NR_IOBUS_DEVS 6
> +#define NR_IOBUS_DEVS 200
> struct kvm_io_device *devs[NR_IOBUS_DEVS];
> };
>
>
>
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