Re: [Qemu-devel] slow virtio network with vhost=on and multiple cores

[Jan Kiszka <jan.kiszka@web.de>]

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On 2012-11-06 10:01, Dietmar Maurer wrote:
> OK, bisect point me to this commit:
> 
> # git bisect bad
> 7d37d351dffee60fc7048bbfd8573421f15eb724 is the first bad commit
> commit 7d37d351dffee60fc7048bbfd8573421f15eb724
> Author: Jan Kiszka <jan.kiszka@siemens.com>
> Date:   Thu May 17 10:32:39 2012 -0300
> 
>     virtio/vhost: Add support for KVM in-kernel MSI injection
>     
>     Make use of the new vector notifier to track changes of the MSI-X
>     configuration of virtio PCI devices. On enabling events, we establish
>     the required virtual IRQ to MSI-X message route and link the signaling
>     eventfd file descriptor to this vIRQ line. That way, vhost-generated
>     interrupts can be directly delivered to an in-kernel MSI-X consumer like
>     the x86 APIC.
>     
>     Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
>     Signed-off-by: Avi Kivity <avi@redhat.com>
> 
> :040000 040000 1734ddc60cd8a85c7187e93e5a4c02e6d7706cf8 f417e63a684f3b92f5ff35d256962a2490890f00 M	hw
> 
> 
> This obviously breaks vhost when using multiple cores.

With "obviously" you mean you already have a clue why?

I'll try to reproduce.

Jan



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