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Re: [Qemu-devel] slow virtio network with vhost=on and multiple cores
From: |
Dietmar Maurer |
Subject: |
Re: [Qemu-devel] slow virtio network with vhost=on and multiple cores |
Date: |
Tue, 6 Nov 2012 09:01:37 +0000 |
OK, bisect point me to this commit:
# git bisect bad
7d37d351dffee60fc7048bbfd8573421f15eb724 is the first bad commit
commit 7d37d351dffee60fc7048bbfd8573421f15eb724
Author: Jan Kiszka <address@hidden>
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 <address@hidden>
Signed-off-by: Avi Kivity <address@hidden>
:040000 040000 1734ddc60cd8a85c7187e93e5a4c02e6d7706cf8
f417e63a684f3b92f5ff35d256962a2490890f00 M hw
This obviously breaks vhost when using multiple cores.
> -----Original Message-----
> From: Peter Lieven [mailto:address@hidden
> Sent: Dienstag, 06. November 2012 08:47
> To: Dietmar Maurer
> Cc: Stefan Hajnoczi; address@hidden; Michael S. Tsirkin
> Subject: Re: [Qemu-devel] slow virtio network with vhost=on and multiple
> cores
>
> Dietmar Maurer wrote:
> >> > ./x86_64-softmmu/qemu-system-x86_64 -smp sockets=1,cores=2 -m
> 512 -
> >> hda
> >> > debian-squeeze-netinst.raw -netdev
> >> > type=tap,id=net0,ifname=tap111i0,vhost=on -device
> >> > virtio-net-pci,netdev=net0,id=net0
> >> >
> >> > Downloading a larger file with wget inside the guest will show the
> >> problem.
> >> Speed drops from 100MB/s to 15MB/s.
> >> >
> >> > Can someone reproduce that bug? Any ideas how to fix that?
> >>
> >> Which exact QEMU are you using: qemu or qemu-kvm? Distro package or
> >> from source? Any patches applied?
> >
> > I just tested with latest sources from
> > git://git.qemu-project.org/qemu.git
> >
> > ./x86_64-softmmu/qemu-system-x86_64 -smp sockets=1,cores=2 -m 512 -
> hda
> > debian-squeeze-netinst.raw -netdev
> > type=tap,id=net0,ifname=tap111i0,vhost=on -device
> > virtio-net-pci,netdev=net0,id=net0 --enable-kvm
> >
> > got incredible bad performance - can't you reproduce the problem?
>
> I have seen a similar problem, ...
- [Qemu-devel] slow virtio network with vhost=on and multiple cores, Dietmar Maurer, 2012/11/05
- Re: [Qemu-devel] slow virtio network with vhost=on and multiple cores, Stefan Hajnoczi, 2012/11/05
- Re: [Qemu-devel] slow virtio network with vhost=on and multiple cores, Dietmar Maurer, 2012/11/05
- Re: [Qemu-devel] slow virtio network with vhost=on and multiple cores, Dietmar Maurer, 2012/11/06
- Re: [Qemu-devel] slow virtio network with vhost=on and multiple cores, Peter Lieven, 2012/11/06
- Re: [Qemu-devel] slow virtio network with vhost=on and multiple cores, Dietmar Maurer, 2012/11/06
- Re: [Qemu-devel] slow virtio network with vhost=on and multiple cores,
Dietmar Maurer <=
- Re: [Qemu-devel] slow virtio network with vhost=on and multiple cores, Jan Kiszka, 2012/11/06
- Re: [Qemu-devel] slow virtio network with vhost=on and multiple cores, Dietmar Maurer, 2012/11/06
- Re: [Qemu-devel] slow virtio network with vhost=on and multiple cores, Jan Kiszka, 2012/11/06
- Re: [Qemu-devel] slow virtio network with vhost=on and multiple cores, Dietmar Maurer, 2012/11/06
- Re: [Qemu-devel] slow virtio network with vhost=on and multiple cores, Jan Kiszka, 2012/11/08
- Re: [Qemu-devel] slow virtio network with vhost=on and multiple cores, Peter Lieven, 2012/11/08
- Re: [Qemu-devel] slow virtio network with vhost=on and multiple cores, Dietmar Maurer, 2012/11/08
- Re: [Qemu-devel] slow virtio network with vhost=on and multiple cores, Peter Lieven, 2012/11/08
- Re: [Qemu-devel] slow virtio network with vhost=on and multiple cores, Dietmar Maurer, 2012/11/09
- Re: [Qemu-devel] slow virtio network with vhost=on and multiple cores, Peter Lieven, 2012/11/09