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Subject[ PATCH 3/3] vhost: make it more scalable by creating a vhost thread per device
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Make vhost more scalable by creating a separate vhost thread per
vhost device. This provides better scaling across virtio-net interfaces
in multiple guests.

Also attach each vhost thread to the cgroup and cpumask of the
associated guest(qemu or libvirt).

Signed-off-by: Sridhar Samudrala <sri@us.ibm.com>

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 9777583..18bf5be 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -329,19 +329,22 @@ static void handle_rx_net(struct work_struct *work)
static int vhost_net_open(struct inode *inode, struct file *f)
{
struct vhost_net *n = kmalloc(sizeof *n, GFP_KERNEL);
+ struct vhost_dev *dev;
int r;
if (!n)
return -ENOMEM;
+
+ dev = &n->dev;
n->vqs[VHOST_NET_VQ_TX].handle_kick = handle_tx_kick;
n->vqs[VHOST_NET_VQ_RX].handle_kick = handle_rx_kick;
- r = vhost_dev_init(&n->dev, n->vqs, VHOST_NET_VQ_MAX);
+ r = vhost_dev_init(dev, n->vqs, VHOST_NET_VQ_MAX);
if (r < 0) {
kfree(n);
return r;
}

- vhost_poll_init(n->poll + VHOST_NET_VQ_TX, handle_tx_net, POLLOUT);
- vhost_poll_init(n->poll + VHOST_NET_VQ_RX, handle_rx_net, POLLIN);
+ vhost_poll_init(n->poll + VHOST_NET_VQ_TX, handle_tx_net, POLLOUT, dev);
+ vhost_poll_init(n->poll + VHOST_NET_VQ_RX, handle_rx_net, POLLIN, dev);
n->tx_poll_state = VHOST_NET_POLL_DISABLED;

f->private_data = n;
@@ -644,25 +647,14 @@ static struct miscdevice vhost_net_misc = {

int vhost_net_init(void)
{
- int r = vhost_init();
- if (r)
- goto err_init;
- r = misc_register(&vhost_net_misc);
- if (r)
- goto err_reg;
- return 0;
-err_reg:
- vhost_cleanup();
-err_init:
- return r;
-
+ return misc_register(&vhost_net_misc);
}
+
module_init(vhost_net_init);

void vhost_net_exit(void)
{
misc_deregister(&vhost_net_misc);
- vhost_cleanup();
}
module_exit(vhost_net_exit);

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 49fa953..b076b9b 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -37,8 +37,6 @@ enum {
VHOST_MEMORY_F_LOG = 0x1,
};

-static struct workqueue_struct *vhost_workqueue;
-
static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
poll_table *pt)
{
@@ -57,18 +55,19 @@ static int vhost_poll_wakeup(wait_queue_t *wait, unsigned mode, int sync,
if (!((unsigned long)key & poll->mask))
return 0;

- queue_work(vhost_workqueue, &poll->work);
+ queue_work(poll->dev->wq, &poll->work);
return 0;
}

/* Init poll structure */
void vhost_poll_init(struct vhost_poll *poll, work_func_t func,
- unsigned long mask)
+ unsigned long mask, struct vhost_dev *dev)
{
INIT_WORK(&poll->work, func);
init_waitqueue_func_entry(&poll->wait, vhost_poll_wakeup);
init_poll_funcptr(&poll->table, vhost_poll_func);
poll->mask = mask;
+ poll->dev = dev;
}

/* Start polling a file. We add ourselves to file's wait queue. The caller must
@@ -97,7 +96,7 @@ void vhost_poll_flush(struct vhost_poll *poll)

void vhost_poll_queue(struct vhost_poll *poll)
{
- queue_work(vhost_workqueue, &poll->work);
+ queue_work(poll->dev->wq, &poll->work);
}

static void vhost_vq_reset(struct vhost_dev *dev,
@@ -129,6 +128,13 @@ long vhost_dev_init(struct vhost_dev *dev,
struct vhost_virtqueue *vqs, int nvqs)
{
int i;
+ char vhost_name[20];
+
+ snprintf(vhost_name, 20, "vhost-%d", current->pid);
+ dev->wq = create_singlethread_workqueue_in_current_cg(vhost_name);
+ if (!dev->wq)
+ return -ENOMEM;
+
dev->vqs = vqs;
dev->nvqs = nvqs;
mutex_init(&dev->mutex);
@@ -144,7 +150,7 @@ long vhost_dev_init(struct vhost_dev *dev,
if (dev->vqs[i].handle_kick)
vhost_poll_init(&dev->vqs[i].poll,
dev->vqs[i].handle_kick,
- POLLIN);
+ POLLIN, dev);
}
return 0;
}
@@ -217,6 +223,8 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
if (dev->mm)
mmput(dev->mm);
dev->mm = NULL;
+
+ destroy_workqueue(dev->wq);
}

static int log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
@@ -1105,16 +1113,3 @@ void vhost_disable_notify(struct vhost_virtqueue *vq)
vq_err(vq, "Failed to enable notification at %p: %d\n",
&vq->used->flags, r);
}
-
-int vhost_init(void)
-{
- vhost_workqueue = create_singlethread_workqueue("vhost");
- if (!vhost_workqueue)
- return -ENOMEM;
- return 0;
-}
-
-void vhost_cleanup(void)
-{
- destroy_workqueue(vhost_workqueue);
-}
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 44591ba..60fefd0 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -29,10 +29,11 @@ struct vhost_poll {
/* struct which will handle all actual work. */
struct work_struct work;
unsigned long mask;
+ struct vhost_dev *dev;
};

void vhost_poll_init(struct vhost_poll *poll, work_func_t func,
- unsigned long mask);
+ unsigned long mask, struct vhost_dev *dev);
void vhost_poll_start(struct vhost_poll *poll, struct file *file);
void vhost_poll_stop(struct vhost_poll *poll);
void vhost_poll_flush(struct vhost_poll *poll);
@@ -110,6 +111,7 @@ struct vhost_dev {
int nvqs;
struct file *log_file;
struct eventfd_ctx *log_ctx;
+ struct workqueue_struct *wq;
};

long vhost_dev_init(struct vhost_dev *, struct vhost_virtqueue *vqs, int nvqs);
@@ -136,9 +138,6 @@ bool vhost_enable_notify(struct vhost_virtqueue *);
int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
unsigned int log_num, u64 len);

-int vhost_init(void);
-void vhost_cleanup(void);
-
#define vq_err(vq, fmt, ...) do { \
pr_debug(pr_fmt(fmt), ##__VA_ARGS__); \
if ((vq)->error_ctx) \



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