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Subject[RFC PATCH 3/3] virtio-net: using single MSIX irq for each TX/RX queue pair
Date
This patch try to reduce the number of MSIX irqs required for
virtio-net by sharing a MSIX irq for each TX/RX queue pair through
channels. If transport support channel, about half of the MSIX irqs
were reduced.

Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
drivers/net/virtio_net.c | 26 +++++++++++++++++++++++++-
1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 3ba3499..03a0c28 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -72,6 +72,9 @@ struct send_queue {

/* Name of the send queue: output.$index */
char name[40];
+
+ /* Name of the channel, share with rxq */
+ char channel_name[40];
};

/* Internal representation of a receive virtqueue */
@@ -1522,6 +1525,8 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
int ret = -ENOMEM;
int i, total_vqs;
const char **names;
+ const char **channel_names;
+ unsigned *channels;

/* We expect 1 RX virtqueue followed by 1 TX virtqueue, followed by
* possible N-1 RX/TX queue pairs used in multiqueue mode, followed by
@@ -1540,6 +1545,14 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
names = kmalloc(total_vqs * sizeof(*names), GFP_KERNEL);
if (!names)
goto err_names;
+ channel_names = kmalloc_array(vi->max_queue_pairs,
+ sizeof(*channel_names),
+ GFP_KERNEL);
+ if (!channel_names)
+ goto err_channel_names;
+ channels = kmalloc_array(total_vqs, sizeof(*channels), GFP_KERNEL);
+ if (!channels)
+ goto err_channels;

/* Parameters for control virtqueue, if any */
if (vi->has_cvq) {
@@ -1555,10 +1568,15 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
sprintf(vi->sq[i].name, "output.%d", i);
names[rxq2vq(i)] = vi->rq[i].name;
names[txq2vq(i)] = vi->sq[i].name;
+ sprintf(vi->sq[i].channel_name, "txrx.%d", i);
+ channel_names[i] = vi->sq[i].channel_name;
+ channels[rxq2vq(i)] = i;
+ channels[txq2vq(i)] = i;
}

ret = vi->vdev->config->find_vqs(vi->vdev, total_vqs, vqs, callbacks,
- names, NULL, NULL, 0);
+ names, channels, channel_names,
+ vi->max_queue_pairs);
if (ret)
goto err_find;

@@ -1573,6 +1591,8 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
vi->sq[i].vq = vqs[txq2vq(i)];
}

+ kfree(channels);
+ kfree(channel_names);
kfree(names);
kfree(callbacks);
kfree(vqs);
@@ -1580,6 +1600,10 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
return 0;

err_find:
+ kfree(channels);
+err_channels:
+ kfree(channel_names);
+err_channel_names:
kfree(names);
err_names:
kfree(callbacks);
--
1.8.3.1


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