Re: [Qemu-devel] [PATCH] vhost: add trace for IOTLB miss

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Mar 21, 2018 at 11:21:24AM +0800, Peter Xu wrote:
> Add some trace points for IOTLB translation for vhost. After vhost-user
> is setup, the only IO path that QEMU will participate should be the
> IOMMU translation, so it'll be good we can track this with explicit
> timestamps when needed to see how long time we take to do the
> translation, and whether there's anything stuck inside.  It might be
> useful for triaging vhost-user problems.
> 
> Signed-off-by: Peter Xu <peterx@redhat.com>

Could you rebase pls?

> ---
>  hw/virtio/trace-events | 1 +
>  hw/virtio/vhost.c      | 7 +++++++
>  2 files changed, 8 insertions(+)
> 
> diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
> index 742ff0f90b..933eaab133 100644
> --- a/hw/virtio/trace-events
> +++ b/hw/virtio/trace-events
> @@ -5,6 +5,7 @@ vhost_commit(bool started, bool changed) "Started: %d Changed: %d"
>  vhost_region_add_section(const char *name, uint64_t gpa, uint64_t size, uint64_t host) "%s: 0x%"PRIx64"+0x%"PRIx64" @ 0x%"PRIx64
>  vhost_region_add_section_abut(const char *name, uint64_t new_size) "%s: 0x%"PRIx64
>  vhost_section(const char *name, int r) "%s:%d"
> +vhost_iotlb_miss(void *dev, int step) "%p step %d"
>  
>  # hw/virtio/virtio.c
>  virtqueue_alloc_element(void *elem, size_t sz, unsigned in_num, unsigned out_num) "elem %p size %zd in_num %u out_num %u"
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index d8d0ef92e1..aa68f79510 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -839,12 +839,15 @@ int vhost_device_iotlb_miss(struct vhost_dev *dev, uint64_t iova, int write)
>  
>      rcu_read_lock();
>  
> +    trace_vhost_iotlb_miss(dev, 1);
> +
>      iotlb = address_space_get_iotlb_entry(dev->vdev->dma_as,
>                                            iova, write);
>      if (iotlb.target_as != NULL) {
>          ret = vhost_memory_region_lookup(dev, iotlb.translated_addr,
>                                           &uaddr, &len);
>          if (ret) {
> +            trace_vhost_iotlb_miss(dev, 3);
>              error_report("Fail to lookup the translated address "
>                           "%"PRIx64, iotlb.translated_addr);
>              goto out;
> @@ -856,10 +859,14 @@ int vhost_device_iotlb_miss(struct vhost_dev *dev, uint64_t iova, int write)
>          ret = vhost_backend_update_device_iotlb(dev, iova, uaddr,
>                                                  len, iotlb.perm);
>          if (ret) {
> +            trace_vhost_iotlb_miss(dev, 4);
>              error_report("Fail to update device iotlb");
>              goto out;
>          }
>      }
> +
> +    trace_vhost_iotlb_miss(dev, 2);
> +
>  out:
>      rcu_read_unlock();
>  
> -- 
> 2.14.3