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    Subject[PATCH UPDATED 1/3] 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.

    Signed-off-by: Tejun Heo <tj@kernel.org>
    Cc: Michael S. Tsirkin <mst@redhat.com>
    Cc: Sridhar Samudrala <samudrala.sridhar@gmail.com>
    ---
    Okay, just tested it. dev->work_lock had to be updated to use irq
    operations but other than that it worked just fine. Copied a large
    file using scp and it seems to perform pretty well although I don't
    have any reference of comparison. So, here's the updated version with
    the sign off.

    Thanks.

    drivers/vhost/net.c | 56 ++++++++++---------------
    drivers/vhost/vhost.c | 111 ++++++++++++++++++++++++++++++++++++++------------
    drivers/vhost/vhost.h | 38 +++++++++++------
    3 files changed, 134 insertions(+), 71 deletions(-)

    Index: work/drivers/vhost/net.c
    ===================================================================
    --- work.orig/drivers/vhost/net.c
    +++ work/drivers/vhost/net.c
    @@ -294,54 +294,58 @@ static void handle_rx(struct vhost_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;
    @@ -644,25 +648,13 @@ 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);

    Index: work/drivers/vhost/vhost.c
    ===================================================================
    --- work.orig/drivers/vhost/vhost.c
    +++ work/drivers/vhost/vhost.c
    @@ -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
    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);
    + atomic_set(&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 +98,29 @@ void vhost_poll_stop(struct vhost_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;
    + int seq = work->queue_seq;
    +
    + atomic_inc(&work->flushing);
    + smp_mb__after_atomic_inc(); /* mb flush-b0 paired with worker-b1 */
    + wait_event(work->done, seq - work->done_seq <= 0);
    + atomic_dec(&work->flushing);
    + smp_mb__after_atomic_dec(); /* rmb flush-b1 paired with worker-b0 */
    }

    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 +148,52 @@ static void vhost_vq_reset(struct vhost_
    vq->log_ctx = NULL;
    }

    +static int vhost_worker(void *data)
    +{
    + struct vhost_dev *dev = data;
    + struct vhost_work *work;
    +
    +repeat:
    + set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
    +
    + if (kthread_should_stop()) {
    + __set_current_state(TASK_RUNNING);
    + return 0;
    + }
    +
    + work = NULL;
    + spin_lock_irq(&dev->work_lock);
    + if (!list_empty(&dev->work_list)) {
    + work = list_first_entry(&dev->work_list,
    + struct vhost_work, node);
    + list_del_init(&work->node);
    + }
    + spin_unlock_irq(&dev->work_lock);
    +
    + if (work) {
    + __set_current_state(TASK_RUNNING);
    + work->fn(work);
    + smp_wmb(); /* wmb worker-b0 paired with flush-b1 */
    + work->done_seq = work->queue_seq;
    + smp_mb(); /* mb worker-b1 paired with flush-b0 */
    + if (atomic_read(&work->flushing))
    + wake_up_all(&work->done);
    + } else
    + schedule();
    +
    + goto repeat;
    +}
    +
    long vhost_dev_init(struct vhost_dev *dev,
    struct vhost_virtqueue *vqs, int nvqs)
    {
    + struct task_struct *worker;
    int i;
    +
    + worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);
    + if (IS_ERR(worker))
    + return PTR_ERR(worker);
    +
    dev->vqs = vqs;
    dev->nvqs = nvqs;
    mutex_init(&dev->mutex);
    @@ -136,6 +201,9 @@ long vhost_dev_init(struct vhost_dev *de
    dev->log_file = NULL;
    dev->memory = NULL;
    dev->mm = NULL;
    + spin_lock_init(&dev->work_lock);
    + INIT_LIST_HEAD(&dev->work_list);
    + dev->worker = worker;

    for (i = 0; i < dev->nvqs; ++i) {
    dev->vqs[i].dev = dev;
    @@ -143,9 +211,10 @@ long vhost_dev_init(struct vhost_dev *de
    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);
    }
    +
    + wake_up_process(worker); /* avoid contributing to loadavg */
    return 0;
    }

    @@ -217,6 +286,9 @@ void vhost_dev_cleanup(struct vhost_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)
    @@ -1113,16 +1185,3 @@ void vhost_disable_notify(struct vhost_v
    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);
    -}
    Index: work/drivers/vhost/vhost.h
    ===================================================================
    --- work.orig/drivers/vhost/vhost.h
    +++ work/drivers/vhost/vhost.h
    @@ -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;
    + atomic_t flushing;
    + int queue_seq;
    + int 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_vi
    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) \

    \
     
     \ /
      Last update: 2010-06-02 20:43    [W:0.049 / U:29.980 seconds]
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