doc: improve vhost zero copy guide

Highlight that vhost zero copy mbufs should be consumed
as soon as possible.

Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

diff --git a/doc/guides/prog_guide/vhost_lib.rst b/doc/guides/prog_guide/vhost_lib.rst
index c77df33..a86c07a 100644 (file)
--- a/doc/guides/prog_guide/vhost_lib.rst
+++ b/doc/guides/prog_guide/vhost_lib.rst
@@ -92,6 +92,9 @@ The following is an overview of some key Vhost API functions:
       to use vfio-pci driver, please insert vfio-pci kernel module in noiommu
       mode.
 
+    * The consumer of zero copy mbufs should consume these mbufs as soon as
+      possible, otherwise it may block the operations in vhost.
+
   - ``RTE_VHOST_USER_IOMMU_SUPPORT``
 
     IOMMU support will be enabled when this flag is set. It is disabled by