From mboxrd@z Thu Jan  1 00:00:00 1970
From: Pekka Enberg <penberg@kernel.org>
Subject: Re: [PATCH 1/3] kvm tools: Make virtio-net kvm__irq_line thread safe
Date: Fri, 29 Apr 2011 09:52:02 +0300
Message-ID: <BANLkTikn8JM33gRCsODgKWPyq7UZPjdL6g@mail.gmail.com>
References: <1304058985-13833-1-git-send-email-asias.hejun@gmail.com>
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Cc: Cyrill Gorcunov <gorcunov@gmail.com>, Ingo Molnar <mingo@elte.hu>,
	Sasha Levin <levinsasha928@gmail.com>,
	Prasad Joshi <prasadjoshi124@gmail.com>, kvm@vger.kernel.org
To: Asias He <asias.hejun@gmail.com>
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On Fri, Apr 29, 2011 at 9:36 AM, Asias He <asias.hejun@gmail.com> wrote=
:
> This patch fixes virtio-net randmom stall
>
> host $ scp guest:/root/big.guest .
> big.guest 42% =A0440MB =A067.7KB/s - stalled -
>
> Signed-off-by: Asias He <asias.hejun@gmail.com>
> ---
> =A0tools/kvm/virtio-net.c | =A0 =A09 +++++++--
> =A01 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/tools/kvm/virtio-net.c b/tools/kvm/virtio-net.c
> index 58b3de4..efe06cb 100644
> --- a/tools/kvm/virtio-net.c
> +++ b/tools/kvm/virtio-net.c
> @@ -77,9 +77,12 @@ static void virtio_net_rx_callback(struct kvm *sel=
f, void *param)
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0head =3D virt_queue__get_iov(vq, iov, =
&out, &in, self);
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0len =3D readv(net_device.tap_fd, iov, =
in);
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0virt_queue__set_used_elem(vq, head, le=
n);
> - =A0 =A0 =A0 }
>
> - =A0 =A0 =A0 kvm__irq_line(self, VIRTIO_NET_IRQ, 1);
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 /* We should interrupt guest right now,=
 otherwise latency is huge. */
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 mutex_lock(&net_device.mutex);
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 kvm__irq_line(self, VIRTIO_NET_IRQ, 1);
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 mutex_unlock(&net_device.mutex);
> + =A0 =A0 =A0 }
> =A0}
>
> =A0static void virtio_net_tx_callback(struct kvm *self, void *param)

Please make that IRQ latency fix a separate patch. Don't we need to do
it for TX path as well, btw?