Re: [PATCH V8 1/3] virtio-net: fix the set affinity bug when CPU IDs are not consecutive
From: Wanlong Gao Date: Fri, 25 Jan 2013 17:51:29 +0800 > As Michael mentioned, set affinity and select queue will not work very > well when CPU IDs are not consecutive, this can happen with hot unplug. > Fix this bug by traversal the online CPUs, and create a per cpu variable > to find the mapping from CPU to the preferable virtual-queue. > > Cc: Rusty Russell > Cc: "Michael S. Tsirkin" > Cc: Jason Wang > Cc: Eric Dumazet > Cc: "David S. Miller" > Cc: virtualizat...@lists.linux-foundation.org > Cc: net...@vger.kernel.org > Signed-off-by: Wanlong Gao > Acked-by: Michael S. Tsirkin Applied. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH V8 1/3] virtio-net: fix the set affinity bug when CPU IDs are not consecutive
From: Wanlong Gao gaowanl...@cn.fujitsu.com Date: Fri, 25 Jan 2013 17:51:29 +0800 As Michael mentioned, set affinity and select queue will not work very well when CPU IDs are not consecutive, this can happen with hot unplug. Fix this bug by traversal the online CPUs, and create a per cpu variable to find the mapping from CPU to the preferable virtual-queue. Cc: Rusty Russell ru...@rustcorp.com.au Cc: Michael S. Tsirkin m...@redhat.com Cc: Jason Wang jasow...@redhat.com Cc: Eric Dumazet erdnet...@gmail.com Cc: David S. Miller da...@davemloft.net Cc: virtualizat...@lists.linux-foundation.org Cc: net...@vger.kernel.org Signed-off-by: Wanlong Gao gaowanl...@cn.fujitsu.com Acked-by: Michael S. Tsirkin m...@redhat.com Applied. -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH V8 1/3] virtio-net: fix the set affinity bug when CPU IDs are not consecutive
As Michael mentioned, set affinity and select queue will not work very
well when CPU IDs are not consecutive, this can happen with hot unplug.
Fix this bug by traversal the online CPUs, and create a per cpu variable
to find the mapping from CPU to the preferable virtual-queue.
Cc: Rusty Russell
Cc: "Michael S. Tsirkin"
Cc: Jason Wang
Cc: Eric Dumazet
Cc: "David S. Miller"
Cc: virtualizat...@lists.linux-foundation.org
Cc: net...@vger.kernel.org
Signed-off-by: Wanlong Gao
Acked-by: Michael S. Tsirkin
---
V7->V8:
set vq index unconditionally, make bisect happy,
make sure don't introduce bug. (Jason)
V6->V7:
serialize virtnet_set_queues to avoid a race with cpu hotplug (Jason)
V5->V6:
remove {get|put}_online_cpus from virtnet_del_vqs (Jason)
V4->V5:
Add get/put_online_cpus to avoid CPUs go up and down during operations
(Rusty)
V3->V4:
move vq_index into virtnet_info (Jason)
change the mapping value when not setting affinity (Jason)
address the comments about select_queue (Rusty)
drivers/net/virtio_net.c | 67 ++--
1 file changed, 54 insertions(+), 13 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index a6fcf15..fda214a 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -123,6 +123,9 @@ struct virtnet_info {
/* Does the affinity hint is set for virtqueues? */
bool affinity_hint_set;
+
+ /* Per-cpu variable to show the mapping from CPU to virtqueue */
+ int __percpu *vq_index;
};
struct skb_vnet_hdr {
@@ -1016,6 +1019,7 @@ static int virtnet_vlan_rx_kill_vid(struct net_device
*dev, u16 vid)
static void virtnet_set_affinity(struct virtnet_info *vi, bool set)
{
int i;
+ int cpu;
/* In multiqueue mode, when the number of cpu is equal to the number of
* queue pairs, we let the queue pairs to be private to one cpu by
@@ -1023,22 +1027,40 @@ static void virtnet_set_affinity(struct virtnet_info
*vi, bool set)
*/
if ((vi->curr_queue_pairs == 1 ||
vi->max_queue_pairs != num_online_cpus()) && set) {
- if (vi->affinity_hint_set)
+ if (vi->affinity_hint_set) {
set = false;
- else
+ } else {
+ i = 0;
+ for_each_online_cpu(cpu)
+ *per_cpu_ptr(vi->vq_index, cpu) =
+ ++i % vi->curr_queue_pairs;
return;
+ }
}
- for (i = 0; i < vi->max_queue_pairs; i++) {
- int cpu = set ? i : -1;
- virtqueue_set_affinity(vi->rq[i].vq, cpu);
- virtqueue_set_affinity(vi->sq[i].vq, cpu);
- }
+ if (set) {
+ i = 0;
+ for_each_online_cpu(cpu) {
+ virtqueue_set_affinity(vi->rq[i].vq, cpu);
+ virtqueue_set_affinity(vi->sq[i].vq, cpu);
+ *per_cpu_ptr(vi->vq_index, cpu) = i;
+ i++;
+ }
- if (set)
vi->affinity_hint_set = true;
- else
+ } else {
+ for(i = 0; i < vi->max_queue_pairs; i++) {
+ virtqueue_set_affinity(vi->rq[i].vq, -1);
+ virtqueue_set_affinity(vi->sq[i].vq, -1);
+ }
+
+ i = 0;
+ for_each_online_cpu(cpu)
+ *per_cpu_ptr(vi->vq_index, cpu) =
+ ++i % vi->curr_queue_pairs;
+
vi->affinity_hint_set = false;
+ }
}
static void virtnet_get_ringparam(struct net_device *dev,
@@ -1082,6 +1104,7 @@ static int virtnet_set_channels(struct net_device *dev,
if (queue_pairs > vi->max_queue_pairs)
return -EINVAL;
+ get_online_cpus();
err = virtnet_set_queues(vi, queue_pairs);
if (!err) {
netif_set_real_num_tx_queues(dev, queue_pairs);
@@ -1089,6 +1112,7 @@ static int virtnet_set_channels(struct net_device *dev,
virtnet_set_affinity(vi, true);
}
+ put_online_cpus();
return err;
}
@@ -1127,12 +1151,19 @@ static int virtnet_change_mtu(struct net_device *dev,
int new_mtu)
/* To avoid contending a lock hold by a vcpu who would exit to host, select the
* txq based on the processor id.
- * TODO: handle cpu hotplug.
*/
static u16 virtnet_select_queue(struct net_device *dev, struct sk_buff *skb)
{
- int txq = skb_rx_queue_recorded(skb) ? skb_get_rx_queue(skb) :
- smp_processor_id();
+ int txq;
+ struct virtnet_info *vi = netdev_priv(dev);
+
+ if (skb_rx_queue_recorded(skb)) {
+ txq = skb_get_rx_queue(skb);
+ } else {
+ txq = *__this_cpu_ptr(vi->vq_index);
+ if
[PATCH V8 1/3] virtio-net: fix the set affinity bug when CPU IDs are not consecutive
As Michael mentioned, set affinity and select queue will not work very
well when CPU IDs are not consecutive, this can happen with hot unplug.
Fix this bug by traversal the online CPUs, and create a per cpu variable
to find the mapping from CPU to the preferable virtual-queue.
Cc: Rusty Russell ru...@rustcorp.com.au
Cc: Michael S. Tsirkin m...@redhat.com
Cc: Jason Wang jasow...@redhat.com
Cc: Eric Dumazet erdnet...@gmail.com
Cc: David S. Miller da...@davemloft.net
Cc: virtualizat...@lists.linux-foundation.org
Cc: net...@vger.kernel.org
Signed-off-by: Wanlong Gao gaowanl...@cn.fujitsu.com
Acked-by: Michael S. Tsirkin m...@redhat.com
---
V7-V8:
set vq index unconditionally, make bisect happy,
make sure don't introduce bug. (Jason)
V6-V7:
serialize virtnet_set_queues to avoid a race with cpu hotplug (Jason)
V5-V6:
remove {get|put}_online_cpus from virtnet_del_vqs (Jason)
V4-V5:
Add get/put_online_cpus to avoid CPUs go up and down during operations
(Rusty)
V3-V4:
move vq_index into virtnet_info (Jason)
change the mapping value when not setting affinity (Jason)
address the comments about select_queue (Rusty)
drivers/net/virtio_net.c | 67 ++--
1 file changed, 54 insertions(+), 13 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index a6fcf15..fda214a 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -123,6 +123,9 @@ struct virtnet_info {
/* Does the affinity hint is set for virtqueues? */
bool affinity_hint_set;
+
+ /* Per-cpu variable to show the mapping from CPU to virtqueue */
+ int __percpu *vq_index;
};
struct skb_vnet_hdr {
@@ -1016,6 +1019,7 @@ static int virtnet_vlan_rx_kill_vid(struct net_device
*dev, u16 vid)
static void virtnet_set_affinity(struct virtnet_info *vi, bool set)
{
int i;
+ int cpu;
/* In multiqueue mode, when the number of cpu is equal to the number of
* queue pairs, we let the queue pairs to be private to one cpu by
@@ -1023,22 +1027,40 @@ static void virtnet_set_affinity(struct virtnet_info
*vi, bool set)
*/
if ((vi-curr_queue_pairs == 1 ||
vi-max_queue_pairs != num_online_cpus()) set) {
- if (vi-affinity_hint_set)
+ if (vi-affinity_hint_set) {
set = false;
- else
+ } else {
+ i = 0;
+ for_each_online_cpu(cpu)
+ *per_cpu_ptr(vi-vq_index, cpu) =
+ ++i % vi-curr_queue_pairs;
return;
+ }
}
- for (i = 0; i vi-max_queue_pairs; i++) {
- int cpu = set ? i : -1;
- virtqueue_set_affinity(vi-rq[i].vq, cpu);
- virtqueue_set_affinity(vi-sq[i].vq, cpu);
- }
+ if (set) {
+ i = 0;
+ for_each_online_cpu(cpu) {
+ virtqueue_set_affinity(vi-rq[i].vq, cpu);
+ virtqueue_set_affinity(vi-sq[i].vq, cpu);
+ *per_cpu_ptr(vi-vq_index, cpu) = i;
+ i++;
+ }
- if (set)
vi-affinity_hint_set = true;
- else
+ } else {
+ for(i = 0; i vi-max_queue_pairs; i++) {
+ virtqueue_set_affinity(vi-rq[i].vq, -1);
+ virtqueue_set_affinity(vi-sq[i].vq, -1);
+ }
+
+ i = 0;
+ for_each_online_cpu(cpu)
+ *per_cpu_ptr(vi-vq_index, cpu) =
+ ++i % vi-curr_queue_pairs;
+
vi-affinity_hint_set = false;
+ }
}
static void virtnet_get_ringparam(struct net_device *dev,
@@ -1082,6 +1104,7 @@ static int virtnet_set_channels(struct net_device *dev,
if (queue_pairs vi-max_queue_pairs)
return -EINVAL;
+ get_online_cpus();
err = virtnet_set_queues(vi, queue_pairs);
if (!err) {
netif_set_real_num_tx_queues(dev, queue_pairs);
@@ -1089,6 +1112,7 @@ static int virtnet_set_channels(struct net_device *dev,
virtnet_set_affinity(vi, true);
}
+ put_online_cpus();
return err;
}
@@ -1127,12 +1151,19 @@ static int virtnet_change_mtu(struct net_device *dev,
int new_mtu)
/* To avoid contending a lock hold by a vcpu who would exit to host, select the
* txq based on the processor id.
- * TODO: handle cpu hotplug.
*/
static u16 virtnet_select_queue(struct net_device *dev, struct sk_buff *skb)
{
- int txq = skb_rx_queue_recorded(skb) ? skb_get_rx_queue(skb) :
- smp_processor_id();
+ int txq;
+ struct virtnet_info *vi = netdev_priv(dev);
+
+ if (skb_rx_queue_recorded(skb)) {
+ txq =
