Commit c23f3445 authored by Tejun Heo's avatar Tejun Heo Committed by Michael S. Tsirkin
Browse files

vhost: replace vhost_workqueue with per-vhost kthread 



Replace vhost_workqueue with per-vhost kthread.  Other than callback
argument change from struct work_struct * to struct vhost_work *,
there's no visible change to vhost_poll_*() interface.

This conversion is to make each vhost use a dedicated kthread so that
resource control via cgroup can be applied.

Partially based on Sridhar Samudrala's patch.

* Updated to use sub structure vhost_work instead of directly using
  vhost_poll at Michael's suggestion.

* Added flusher wake_up() optimization at Michael's suggestion.

Changes by MST:
* Converted atomics/barrier use to a spinlock.
* Create thread on SET_OWNER
* Fix flushing

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Cc: Sridhar Samudrala <samudrala.sridhar@gmail.com>
parent 4cfa580e

drivers/vhost/net.c

+24 −32
Original line number Diff line number Diff line
@@ -302,54 +302,58 @@ static void handle_rx(struct vhost_net *net) 
	unuse_mm(net->dev.mm);

}



static void handle_tx_kick(struct work_struct *work)

static void handle_tx_kick(struct vhost_work *work)

{

	struct vhost_virtqueue *vq;

	struct vhost_net *net;

	vq = container_of(work, struct vhost_virtqueue, poll.work);

	net = container_of(vq->dev, struct vhost_net, dev);

	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,

						  poll.work);

	struct vhost_net *net = container_of(vq->dev, struct vhost_net, dev);



	handle_tx(net);

}



static void handle_rx_kick(struct work_struct *work)

static void handle_rx_kick(struct vhost_work *work)

{

	struct vhost_virtqueue *vq;

	struct vhost_net *net;

	vq = container_of(work, struct vhost_virtqueue, poll.work);

	net = container_of(vq->dev, struct vhost_net, dev);

	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,

						  poll.work);

	struct vhost_net *net = container_of(vq->dev, struct vhost_net, dev);



	handle_rx(net);

}



static void handle_tx_net(struct work_struct *work)

static void handle_tx_net(struct vhost_work *work)

{

	struct vhost_net *net;

	net = container_of(work, struct vhost_net, poll[VHOST_NET_VQ_TX].work);

	struct vhost_net *net = container_of(work, struct vhost_net,

					     poll[VHOST_NET_VQ_TX].work);

	handle_tx(net);

}



static void handle_rx_net(struct work_struct *work)

static void handle_rx_net(struct vhost_work *work)

{

	struct vhost_net *net;

	net = container_of(work, struct vhost_net, poll[VHOST_NET_VQ_RX].work);

	struct vhost_net *net = container_of(work, struct vhost_net,

					     poll[VHOST_NET_VQ_RX].work);

	handle_rx(net);

}



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;
@@ -656,25 +660,13 @@ static struct miscdevice vhost_net_misc = { 


static 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);



static void vhost_net_exit(void)

{

	misc_deregister(&vhost_net_misc);

	vhost_cleanup();

}

module_exit(vhost_net_exit);

drivers/vhost/vhost.c

+115 −28
Original line number Diff line number Diff line
@@ -17,12 +17,12 @@ 
#include <linux/mm.h>

#include <linux/miscdevice.h>

#include <linux/mutex.h>

#include <linux/workqueue.h>

#include <linux/rcupdate.h>

#include <linux/poll.h>

#include <linux/file.h>

#include <linux/highmem.h>

#include <linux/slab.h>

#include <linux/kthread.h>



#include <linux/net.h>

#include <linux/if_packet.h>
@@ -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)

{
@@ -52,23 +50,31 @@ static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh, 
static int vhost_poll_wakeup(wait_queue_t *wait, unsigned mode, int sync,

			     void *key)

{

	struct vhost_poll *poll;

	poll = container_of(wait, struct vhost_poll, wait);

	struct vhost_poll *poll = container_of(wait, struct vhost_poll, wait);



	if (!((unsigned long)key & poll->mask))

		return 0;



	queue_work(vhost_workqueue, &poll->work);

	vhost_poll_queue(poll);

	return 0;

}



/* Init poll structure */

void vhost_poll_init(struct vhost_poll *poll, work_func_t func,

		     unsigned long mask)

void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,

		     unsigned long mask, struct vhost_dev *dev)

{

	INIT_WORK(&poll->work, func);

	struct vhost_work *work = &poll->work;



	init_waitqueue_func_entry(&poll->wait, vhost_poll_wakeup);

	init_poll_funcptr(&poll->table, vhost_poll_func);

	poll->mask = mask;

	poll->dev = dev;



	INIT_LIST_HEAD(&work->node);

	work->fn = fn;

	init_waitqueue_head(&work->done);

	work->flushing = 0;

	work->queue_seq = work->done_seq = 0;

}



/* Start polling a file. We add ourselves to file's wait queue. The caller must
@@ -92,12 +98,40 @@ void vhost_poll_stop(struct vhost_poll *poll) 
 * locks that are also used by the callback. */

void vhost_poll_flush(struct vhost_poll *poll)

{

	flush_work(&poll->work);

	struct vhost_work *work = &poll->work;

	unsigned seq;

	int left;

	int flushing;



	spin_lock_irq(&poll->dev->work_lock);

	seq = work->queue_seq;

	work->flushing++;

	spin_unlock_irq(&poll->dev->work_lock);

	wait_event(work->done, ({

		   spin_lock_irq(&poll->dev->work_lock);

		   left = seq - work->done_seq <= 0;

		   spin_unlock_irq(&poll->dev->work_lock);

		   left;

	}));

	spin_lock_irq(&poll->dev->work_lock);

	flushing = --work->flushing;

	spin_unlock_irq(&poll->dev->work_lock);

	BUG_ON(flushing < 0);

}



void vhost_poll_queue(struct vhost_poll *poll)

{

	queue_work(vhost_workqueue, &poll->work);

	struct vhost_dev *dev = poll->dev;

	struct vhost_work *work = &poll->work;

	unsigned long flags;



	spin_lock_irqsave(&dev->work_lock, flags);

	if (list_empty(&work->node)) {

		list_add_tail(&work->node, &dev->work_list);

		work->queue_seq++;

		wake_up_process(dev->worker);

	}

	spin_unlock_irqrestore(&dev->work_lock, flags);

}



static void vhost_vq_reset(struct vhost_dev *dev,
@@ -125,10 +159,51 @@ static void vhost_vq_reset(struct vhost_dev *dev, 
	vq->log_ctx = NULL;

}



static int vhost_worker(void *data)

{

	struct vhost_dev *dev = data;

	struct vhost_work *work = NULL;

	unsigned uninitialized_var(seq);



	for (;;) {

		/* mb paired w/ kthread_stop */

		set_current_state(TASK_INTERRUPTIBLE);



		spin_lock_irq(&dev->work_lock);

		if (work) {

			work->done_seq = seq;

			if (work->flushing)

				wake_up_all(&work->done);

		}



		if (kthread_should_stop()) {

			spin_unlock_irq(&dev->work_lock);

			__set_current_state(TASK_RUNNING);

			return 0;

		}

		if (!list_empty(&dev->work_list)) {

			work = list_first_entry(&dev->work_list,

						struct vhost_work, node);

			list_del_init(&work->node);

			seq = work->queue_seq;

		} else

			work = NULL;

		spin_unlock_irq(&dev->work_lock);



		if (work) {

			__set_current_state(TASK_RUNNING);

			work->fn(work);

		} else

			schedule();



	}

}



long vhost_dev_init(struct vhost_dev *dev,

		    struct vhost_virtqueue *vqs, int nvqs)

{

	int i;



	dev->vqs = vqs;

	dev->nvqs = nvqs;

	mutex_init(&dev->mutex);
@@ -136,6 +211,9 @@ long vhost_dev_init(struct vhost_dev *dev, 
	dev->log_file = NULL;

	dev->memory = NULL;

	dev->mm = NULL;

	spin_lock_init(&dev->work_lock);

	INIT_LIST_HEAD(&dev->work_list);

	dev->worker = NULL;



	for (i = 0; i < dev->nvqs; ++i) {

		dev->vqs[i].dev = dev;
@@ -143,9 +221,9 @@ long vhost_dev_init(struct vhost_dev *dev, 
		vhost_vq_reset(dev, dev->vqs + i);

		if (dev->vqs[i].handle_kick)

			vhost_poll_init(&dev->vqs[i].poll,

					dev->vqs[i].handle_kick,

					POLLIN);

					dev->vqs[i].handle_kick, POLLIN, dev);

	}



	return 0;

}
@@ -159,12 +237,31 @@ long vhost_dev_check_owner(struct vhost_dev *dev) 
/* Caller should have device mutex */

static long vhost_dev_set_owner(struct vhost_dev *dev)

{

	struct task_struct *worker;

	int err;

	/* Is there an owner already? */

	if (dev->mm)

		return -EBUSY;

	if (dev->mm) {

		err = -EBUSY;

		goto err_mm;

	}

	/* No owner, become one */

	dev->mm = get_task_mm(current);

	worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);

	if (IS_ERR(worker)) {

		err = PTR_ERR(worker);

		goto err_worker;

	}



	dev->worker = worker;

	wake_up_process(worker);	/* avoid contributing to loadavg */



	return 0;

err_worker:

	if (dev->mm)

		mmput(dev->mm);

	dev->mm = NULL;

err_mm:

	return err;

}



/* Caller should have device mutex */
@@ -217,6 +314,9 @@ void vhost_dev_cleanup(struct vhost_dev *dev) 
	if (dev->mm)

		mmput(dev->mm);

	dev->mm = NULL;



	WARN_ON(!list_empty(&dev->work_list));

	kthread_stop(dev->worker);

}



static int log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
@@ -1115,16 +1215,3 @@ 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);

}

drivers/vhost/vhost.h

+25 −13
Original line number Diff line number Diff line
@@ -5,13 +5,13 @@ 
#include <linux/vhost.h>

#include <linux/mm.h>

#include <linux/mutex.h>

#include <linux/workqueue.h>

#include <linux/poll.h>

#include <linux/file.h>

#include <linux/skbuff.h>

#include <linux/uio.h>

#include <linux/virtio_config.h>

#include <linux/virtio_ring.h>

#include <asm/atomic.h>



struct vhost_device;
@@ -20,19 +20,31 @@ enum { 
	VHOST_NET_MAX_SG = MAX_SKB_FRAGS + 2,

};



struct vhost_work;

typedef void (*vhost_work_fn_t)(struct vhost_work *work);



struct vhost_work {

	struct list_head	  node;

	vhost_work_fn_t		  fn;

	wait_queue_head_t	  done;

	int			  flushing;

	unsigned		  queue_seq;

	unsigned		  done_seq;

};



/* Poll a file (eventfd or socket) */

/* Note: there's nothing vhost specific about this structure. */

struct vhost_poll {

	poll_table                table;

	wait_queue_head_t        *wqh;

	wait_queue_t              wait;

	/* struct which will handle all actual work. */

	struct work_struct        work;

	struct vhost_work	  work;

	unsigned long		  mask;

	struct vhost_dev	 *dev;

};



void vhost_poll_init(struct vhost_poll *poll, work_func_t func,

		     unsigned long mask);

void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,

		     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);
@@ -63,7 +75,7 @@ struct vhost_virtqueue { 
	struct vhost_poll poll;



	/* The routine to call when the Guest pings us, or timeout. */

	work_func_t handle_kick;

	vhost_work_fn_t handle_kick;



	/* Last available index we saw. */

	u16 last_avail_idx;
@@ -86,11 +98,11 @@ struct vhost_virtqueue { 
	struct iovec hdr[VHOST_NET_MAX_SG];

	size_t hdr_size;

	/* We use a kind of RCU to access private pointer.

	 * All readers access it from workqueue, which makes it possible to

	 * flush the workqueue instead of synchronize_rcu. Therefore readers do

	 * All readers access it from worker, which makes it possible to

	 * flush the vhost_work instead of synchronize_rcu. Therefore readers do

	 * not need to call rcu_read_lock/rcu_read_unlock: the beginning of

	 * work item execution acts instead of rcu_read_lock() and the end of

	 * work item execution acts instead of rcu_read_lock().

	 * vhost_work execution acts instead of rcu_read_lock() and the end of

	 * vhost_work execution acts instead of rcu_read_lock().

	 * Writers use virtqueue mutex. */

	void *private_data;

	/* Log write descriptors */
@@ -110,6 +122,9 @@ struct vhost_dev { 
	int nvqs;

	struct file *log_file;

	struct eventfd_ctx *log_ctx;

	spinlock_t work_lock;

	struct list_head work_list;

	struct task_struct *worker;

};



long vhost_dev_init(struct vhost_dev *, struct vhost_virtqueue *vqs, int nvqs);
@@ -136,9 +151,6 @@ 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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