Messages in this thread | | | Subject | Re: [PATCH RFC 03/13] vhost: batching fetches | From | Jason Wang <> | Date | Fri, 5 Jun 2020 11:40:17 +0800 |
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On 2020/6/4 下午4:59, Michael S. Tsirkin wrote: > On Wed, Jun 03, 2020 at 03:27:39PM +0800, Jason Wang wrote: >> On 2020/6/2 下午9:06, Michael S. Tsirkin wrote: >>> With this patch applied, new and old code perform identically. >>> >>> Lots of extra optimizations are now possible, e.g. >>> we can fetch multiple heads with copy_from/to_user now. >>> We can get rid of maintaining the log array. Etc etc. >>> >>> Signed-off-by: Michael S. Tsirkin<mst@redhat.com> >>> Signed-off-by: Eugenio Pérez<eperezma@redhat.com> >>> Link:https://lore.kernel.org/r/20200401183118.8334-4-eperezma@redhat.com >>> Signed-off-by: Michael S. Tsirkin<mst@redhat.com> >>> --- >>> drivers/vhost/test.c | 2 +- >>> drivers/vhost/vhost.c | 47 ++++++++++++++++++++++++++++++++++++++----- >>> drivers/vhost/vhost.h | 5 ++++- >>> 3 files changed, 47 insertions(+), 7 deletions(-) >>> >>> diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c >>> index 9a3a09005e03..02806d6f84ef 100644 >>> --- a/drivers/vhost/test.c >>> +++ b/drivers/vhost/test.c >>> @@ -119,7 +119,7 @@ static int vhost_test_open(struct inode *inode, struct file *f) >>> dev = &n->dev; >>> vqs[VHOST_TEST_VQ] = &n->vqs[VHOST_TEST_VQ]; >>> n->vqs[VHOST_TEST_VQ].handle_kick = handle_vq_kick; >>> - vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX, UIO_MAXIOV, >>> + vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX, UIO_MAXIOV + 64, >>> VHOST_TEST_PKT_WEIGHT, VHOST_TEST_WEIGHT, NULL); >>> f->private_data = n; >>> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c >>> index 8f9a07282625..aca2a5b0d078 100644 >>> --- a/drivers/vhost/vhost.c >>> +++ b/drivers/vhost/vhost.c >>> @@ -299,6 +299,7 @@ static void vhost_vq_reset(struct vhost_dev *dev, >>> { >>> vq->num = 1; >>> vq->ndescs = 0; >>> + vq->first_desc = 0; >>> vq->desc = NULL; >>> vq->avail = NULL; >>> vq->used = NULL; >>> @@ -367,6 +368,11 @@ static int vhost_worker(void *data) >>> return 0; >>> } >>> +static int vhost_vq_num_batch_descs(struct vhost_virtqueue *vq) >>> +{ >>> + return vq->max_descs - UIO_MAXIOV; >>> +} >> 1 descriptor does not mean 1 iov, e.g userspace may pass several 1 byte >> length memory regions for us to translate. >> > Yes but I don't see the relevance. This tells us how many descriptors to > batch, not how many IOVs.
Yes, but questions are:
- this introduce another obstacle to support more than 1K queue size - if we support 1K queue size, does it mean we need to cache 1K descriptors, which seems a large stress on the cache
Thanks
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