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    SubjectRe: [RFC PATCH 1/1] vhost: TX used buffer guest signal accumulation
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    Date
    Resubmit this patch for fixing some minor error (white space, typo).

    Signed-off-by: Shirley Ma <xma@us.ibm.com>
    ---
    drivers/vhost/net.c | 20 +++++++++++++++++++-
    drivers/vhost/vhost.c | 32 ++++++++++++++++++++++++++++++++
    drivers/vhost/vhost.h | 3 +++
    3 files changed, 54 insertions(+), 1 deletions(-)

    diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
    index 4b4da5b..3eb8016 100644
    --- a/drivers/vhost/net.c
    +++ b/drivers/vhost/net.c
    @@ -128,6 +128,7 @@ static void handle_tx(struct vhost_net *net)
    int err, wmem;
    size_t hdr_size;
    struct socket *sock;
    + int max_pend = vq->num - (vq->num >> 2);

    sock = rcu_dereference_check(vq->private_data,
    lockdep_is_held(&vq->mutex));
    @@ -198,7 +199,24 @@ static void handle_tx(struct vhost_net *net)
    if (err != len)
    pr_debug("Truncated TX packet: "
    " len %d != %zd\n", err, len);
    - vhost_add_used_and_signal(&net->dev, vq, head, 0);
    + /*
    + * if no pending buffer size allocate, signal used buffer
    + * one by one, otherwise, signal used buffer when reaching
    + * 3/4 ring size to reduce CPU utilization.
    + */
    + if (unlikely(vq->pend))
    + vhost_add_used_and_signal(&net->dev, vq, head, 0);
    + else {
    + vq->pend[vq->num_pend].id = head;
    + vq->pend[vq->num_pend].len = 0;
    + ++vq->num_pend;
    + if (vq->num_pend == max_pend) {
    + vhost_add_used_and_signal_n(&net->dev, vq,
    + vq->pend,
    + vq->num_pend);
    + vq->num_pend = 0;
    + }
    + }
    total_len += len;
    if (unlikely(total_len >= VHOST_NET_WEIGHT)) {
    vhost_poll_queue(&vq->poll);
    diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
    index 94701ff..f2f3288 100644
    --- a/drivers/vhost/vhost.c
    +++ b/drivers/vhost/vhost.c
    @@ -170,6 +170,16 @@ static void vhost_vq_reset(struct vhost_dev *dev,
    vq->call_ctx = NULL;
    vq->call = NULL;
    vq->log_ctx = NULL;
    + /* signal pending used buffers */
    + if (vq->pend) {
    + if (vq->num_pend != 0) {
    + vhost_add_used_and_signal_n(dev, vq, vq->pend,
    + vq->num_pend);
    + vq->num_pend = 0;
    + }
    + kfree(vq->pend);
    + }
    + vq->pend = NULL;
    }

    static int vhost_worker(void *data)
    @@ -273,7 +283,14 @@ long vhost_dev_init(struct vhost_dev *dev,
    dev->vqs[i].heads = NULL;
    dev->vqs[i].dev = dev;
    mutex_init(&dev->vqs[i].mutex);
    + dev->vqs[i].num_pend = 0;
    + dev->vqs[i].pend = NULL;
    vhost_vq_reset(dev, dev->vqs + i);
    + /* signal 3/4 of ring size used buffers */
    + dev->vqs[i].pend = kmalloc((dev->vqs[i].num -
    + (dev->vqs[i].num >> 2)) *
    + sizeof *dev->vqs[i].pend,
    + GFP_KERNEL);
    if (dev->vqs[i].handle_kick)
    vhost_poll_init(&dev->vqs[i].poll,
    dev->vqs[i].handle_kick, POLLIN, dev);
    @@ -599,6 +616,21 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
    r = -EINVAL;
    break;
    }
    + if (vq->num != s.num) {
    + /* signal used buffers first */
    + if (vq->pend) {
    + if (vq->num_pend != 0) {
    + vhost_add_used_and_signal_n(vq->dev, vq,
    + vq->pend,
    + vq->num_pend);
    + vq->num_pend = 0;
    + }
    + kfree(vq->pend);
    + }
    + /* realloc pending used buffers size */
    + vq->pend = kmalloc((s.num - (s.num >> 2)) *
    + sizeof *vq->pend, GFP_KERNEL);
    + }
    vq->num = s.num;
    break;
    case VHOST_SET_VRING_BASE:
    diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
    index 073d06a..78949c0 100644
    --- a/drivers/vhost/vhost.h
    +++ b/drivers/vhost/vhost.h
    @@ -108,6 +108,9 @@ struct vhost_virtqueue {
    /* Log write descriptors */
    void __user *log_base;
    struct vhost_log *log;
    + /* delay multiple used buffers to signal once */
    + int num_pend;
    + struct vring_used_elem *pend;
    };

    struct vhost_dev {



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