Merge branch 'virtio_net-Expand-affinity-to-arbitrary-numbers-of-cpu-and-vq'

Caleb Raitto says:

====================
virtio_net: Expand affinity to arbitrary numbers of cpu and vq

Virtio-net tries to pin each virtual queue rx and tx interrupt to a cpu if
there are as many queues as cpus.

Expand this heuristic to configure a reasonable affinity setting also
when the number of cpus != the number of virtual queues.

Patch 1 allows vqs to take an affinity mask with more than 1 cpu.
Patch 2 generalizes the algorithm in virtnet_set_affinity beyond
the case where #cpus == #vqs.

v2 changes:
Renamed "virtio_net: Make vp_set_vq_affinity() take a mask." to
"virtio: Make vp_set_vq_affinity() take a mask."

Tested:

[InstanceSetup]
set_multiqueue = false

$ cd /proc/irq
$ for i in `seq 24 60` ; do sudo grep ".*" $i/smp_affinity_list;  done
0-15
0
0
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
10
10
11
11
12
12
13
13
14
14
15
15
0-15
0-15
0-15
0-15

$ cd /sys/class/net/eth0/queues/
$ for i in `seq 0 15` ; do sudo grep ".*" tx-$i/xps_cpus; done
0001
0002
0004
0008
0010
0020
0040
0080
0100
0200
0400
0800
1000
2000
4000
8000

$ sudo ethtool -L eth0 combined 15

$ cd /proc/irq
$ for i in `seq 24 60` ; do sudo grep ".*" $i/smp_affinity_list;  done
0-15
0-1
0-1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
10
10
11
11
12
12
13
13
14
14
15
15
15
15
0-15
0-15
0-15
0-15

$ cd /sys/class/net/eth0/queues/
$ for i in `seq 0 14` ; do sudo grep ".*" tx-$i/xps_cpus; done
0003
0004
0008
0010
0020
0040
0080
0100
0200
0400
0800
1000
2000
4000
8000

$ sudo ethtool -L eth0 combined 8

$ cd /proc/irq
$ for i in `seq 24 60` ; do sudo grep ".*" $i/smp_affinity_list;  done
0-15
0-1
0-1
2-3
2-3
4-5
4-5
6-7
6-7
8-9
8-9
10-11
10-11
12-13
12-13
14-15
14-15
9
9
10
10
11
11
12
12
13
13
14
14
15
15
15
15
0-15
0-15
0-15
0-15

$ cd /sys/class/net/eth0/queues/
$ for i in `seq 0 7` ; do sudo grep ".*" tx-$i/xps_cpus; done
0003
000c
0030
00c0
0300
0c00
3000
c000

$ sudo ethtool -L eth0 combined 16
$ sudo sh -c "echo 0 > /sys/devices/system/cpu/cpu15/online"

$ cd /proc/irq
$ for i in `seq 24 60` ; do sudo grep ".*" $i/smp_affinity_list;  done
0-15
0
0
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
9
10
10
11
11
12
12
13
13
14
14
0
0
0-15
0-15
0-15
0-15

$ cd /sys/class/net/eth0/queues/
$ for i in `seq 0 15` ; do sudo grep ".*" tx-$i/xps_cpus; done
0001
0002
0004
0008
0010
0020
0040
0080
0100
0200
0400
0800
1000
2000
4000
0001

$ for i in `seq 8 15`; \
do sudo sh -c "echo 0 > /sys/devices/system/cpu/cpu$i/online"; done

$ cd /proc/irq
$ for i in `seq 24 60` ; do sudo grep ".*" $i/smp_affinity_list;  done
0-15
0
0
1
1
2
2
3
3
4
4
5
5
6
6
7
7
0
0
1
1
2
2
3
3
4
4
5
5
6
6
7
7
0-15
0-15
0-15
0-15

$ cd /sys/class/net/eth0/queues/
$ for i in `seq 0 15` ; do sudo grep ".*" tx-$i/xps_cpus; done
0001
0002
0004
0008
0010
0020
0040
0080
0001
0002
0004
0008
0010
0020
0040
0080
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 35 insertions, 24 deletions

diff --git a/drivers/crypto/virtio/virtio_crypto_core.c b/drivers/crypto/virtio/virtio_crypto_core.c
index 83326986c113..7c7198553699 100644
--- a/drivers/crypto/virtio/virtio_crypto_core.c
+++ b/drivers/crypto/virtio/virtio_crypto_core.c
@@ -146,7 +146,7 @@ static void virtcrypto_clean_affinity(struct virtio_crypto *vi, long hcpu)
 
 	if (vi->affinity_hint_set) {
 		for (i = 0; i < vi->max_data_queues; i++)
-			virtqueue_set_affinity(vi->data_vq[i].vq, -1);
+			virtqueue_set_affinity(vi->data_vq[i].vq, NULL);
 
 		vi->affinity_hint_set = false;
 	}
@@ -173,7 +173,7 @@ static void virtcrypto_set_affinity(struct virtio_crypto *vcrypto)
 	 *
 	 */
 	for_each_online_cpu(cpu) {
-		virtqueue_set_affinity(vcrypto->data_vq[i].vq, cpu);
+		virtqueue_set_affinity(vcrypto->data_vq[i].vq, cpumask_of(cpu));
 		if (++i >= vcrypto->max_data_queues)
 			break;
 	}
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 39a7f4452587..eb00ae6ee475 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -31,6 +31,7 @@
 #include <linux/average.h>
 #include <linux/filter.h>
 #include <linux/netdevice.h>
+#include <linux/kernel.h>
 #include <linux/pci.h>
 #include <net/route.h>
 #include <net/xdp.h>
@@ -1878,8 +1879,8 @@ static void virtnet_clean_affinity(struct virtnet_info *vi, long hcpu)
 
 	if (vi->affinity_hint_set) {
 		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);
+			virtqueue_set_affinity(vi->rq[i].vq, NULL);
+			virtqueue_set_affinity(vi->sq[i].vq, NULL);
 		}
 
 		vi->affinity_hint_set = false;
@@ -1888,30 +1889,41 @@ static void virtnet_clean_affinity(struct virtnet_info *vi, long hcpu)
 
 static void virtnet_set_affinity(struct virtnet_info *vi)
 {
-	int i;
-	int cpu;
+	cpumask_var_t mask;
+	int stragglers;
+	int group_size;
+	int i, j, cpu;
+	int num_cpu;
+	int stride;
 
-	/* 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
-	 * setting the affinity hint to eliminate the contention.
-	 */
-	if (vi->curr_queue_pairs == 1 ||
-	    vi->max_queue_pairs != num_online_cpus()) {
+	if (!zalloc_cpumask_var(&mask, GFP_KERNEL)) {
 		virtnet_clean_affinity(vi, -1);
 		return;
 	}
 
-	i = 0;
-	for_each_online_cpu(cpu) {
-		const unsigned long *mask = cpumask_bits(cpumask_of(cpu));
+	num_cpu = num_online_cpus();
+	stride = max_t(int, num_cpu / vi->curr_queue_pairs, 1);
+	stragglers = num_cpu >= vi->curr_queue_pairs ?
+			num_cpu % vi->curr_queue_pairs :
+			0;
+	cpu = cpumask_next(-1, cpu_online_mask);
 
-		virtqueue_set_affinity(vi->rq[i].vq, cpu);
-		virtqueue_set_affinity(vi->sq[i].vq, cpu);
-		__netif_set_xps_queue(vi->dev, mask, i, false);
-		i++;
+	for (i = 0; i < vi->curr_queue_pairs; i++) {
+		group_size = stride + (i < stragglers ? 1 : 0);
+
+		for (j = 0; j < group_size; j++) {
+			cpumask_set_cpu(cpu, mask);
+			cpu = cpumask_next_wrap(cpu, cpu_online_mask,
+						nr_cpu_ids, false);
+		}
+		virtqueue_set_affinity(vi->rq[i].vq, mask);
+		virtqueue_set_affinity(vi->sq[i].vq, mask);
+		__netif_set_xps_queue(vi->dev, cpumask_bits(mask), i, false);
+		cpumask_clear(mask);
 	}
 
 	vi->affinity_hint_set = true;
+	free_cpumask_var(mask);
 }
 
 static int virtnet_cpu_online(unsigned int cpu, struct hlist_node *node)
diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
index 705aebd74e56..465a6f5142cc 100644
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -421,7 +421,7 @@ const char *vp_bus_name(struct virtio_device *vdev)
  * - OR over all affinities for shared MSI
  * - ignore the affinity request if we're using INTX
  */
-int vp_set_vq_affinity(struct virtqueue *vq, int cpu)
+int vp_set_vq_affinity(struct virtqueue *vq, const struct cpumask *cpu_mask)
 {
 	struct virtio_device *vdev = vq->vdev;
 	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
@@ -435,11 +435,10 @@ int vp_set_vq_affinity(struct virtqueue *vq, int cpu)
 	if (vp_dev->msix_enabled) {
 		mask = vp_dev->msix_affinity_masks[info->msix_vector];
 		irq = pci_irq_vector(vp_dev->pci_dev, info->msix_vector);
-		if (cpu == -1)
+		if (!cpu_mask)
 			irq_set_affinity_hint(irq, NULL);
 		else {
-			cpumask_clear(mask);
-			cpumask_set_cpu(cpu, mask);
+			cpumask_copy(mask, cpu_mask);
 			irq_set_affinity_hint(irq, mask);
 		}
 	}
diff --git a/drivers/virtio/virtio_pci_common.h b/drivers/virtio/virtio_pci_common.h
index 135ee3cf7175..02271002c2f3 100644
--- a/drivers/virtio/virtio_pci_common.h
+++ b/drivers/virtio/virtio_pci_common.h
@@ -141,7 +141,7 @@ const char *vp_bus_name(struct virtio_device *vdev);
  * - OR over all affinities for shared MSI
  * - ignore the affinity request if we're using INTX
  */
-int vp_set_vq_affinity(struct virtqueue *vq, int cpu);
+int vp_set_vq_affinity(struct virtqueue *vq, const struct cpumask *cpu_mask);
 
 const struct cpumask *vp_get_vq_affinity(struct virtio_device *vdev, int index);