Re: [PATCH 1/3] kvm tools: Make virtio-net kvm__irq_line thread safe

[Asias He <asias.hejun@gmail.com>]

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On 04/29/2011 03:15 PM, Pekka Enberg wrote:
> On Fri, Apr 29, 2011 at 10:13 AM, Asias He <asias.hejun@gmail.com> wrote:
>> No. We only need it in RX path. Sasha's threadpool patch breaks this.
>> I'm just moving it back.
> 
> OK, cool! Can you send the fix as a separate patch?
> 

Here you go.

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Best Regards,
Asias He

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>From 9c188853435be23ad2a73b5062690eb9f2ff1d25 Mon Sep 17 00:00:00 2001
From: Asias He <asias.hejun@gmail.com>
Date: Fri, 29 Apr 2011 10:43:35 +0800
Subject: [PATCH] kvm tools: Fix virtio-net RX path IRQ latency

The TX path does not need this ;-)

Signed-off-by: Asias He <asias.hejun@gmail.com>
---
 tools/kvm/virtio-net.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/kvm/virtio-net.c b/tools/kvm/virtio-net.c
index 58b3de4..310c061 100644
--- a/tools/kvm/virtio-net.c
+++ b/tools/kvm/virtio-net.c
@@ -77,9 +77,10 @@ static void virtio_net_rx_callback(struct kvm *self, void *param)
 		head = virt_queue__get_iov(vq, iov, &out, &in, self);
 		len = readv(net_device.tap_fd, iov, in);
 		virt_queue__set_used_elem(vq, head, len);
-	}
 
-	kvm__irq_line(self, VIRTIO_NET_IRQ, 1);
+		/* We should interrupt guest right now, otherwise latency is huge. */
+		kvm__irq_line(self, VIRTIO_NET_IRQ, 1);
+	}
 }
 
 static void virtio_net_tx_callback(struct kvm *self, void *param)
-- 
1.7.4.4