doc: add links for build requirements per OS

[dpdk.git] / doc / guides / prog_guide / vhost_lib.rst

diff --git a/doc/guides/prog_guide/vhost_lib.rst b/doc/guides/prog_guide/vhost_lib.rst
index b892eec..dc29229 100644 (file)
--- a/doc/guides/prog_guide/vhost_lib.rst
+++ b/doc/guides/prog_guide/vhost_lib.rst
@@ -51,50 +51,6 @@ The following is an overview of some key Vhost API functions:
     This reconnect option is enabled by default. However, it can be turned off
     by setting this flag.
 
     This reconnect option is enabled by default. However, it can be turned off
     by setting this flag.
 

-  - ``RTE_VHOST_USER_DEQUEUE_ZERO_COPY``
-
-    Dequeue zero copy will be enabled when this flag is set. It is disabled by
-    default.
-
-    There are some truths (including limitations) you might want to know while
-    setting this flag:
-
-    * zero copy is not good for small packets (typically for packet size below
-      512).
-
-    * zero copy is really good for VM2VM case. For iperf between two VMs, the
-      boost could be above 70% (when TSO is enabled).
-
-    * For zero copy in VM2NIC case, guest Tx used vring may be starved if the
-      PMD driver consume the mbuf but not release them timely.
-
-      For example, i40e driver has an optimization to maximum NIC pipeline which
-      postpones returning transmitted mbuf until only tx_free_threshold free
-      descs left. The virtio TX used ring will be starved if the formula
-      (num_i40e_tx_desc - num_virtio_tx_desc > tx_free_threshold) is true, since
-      i40e will not return back mbuf.
-
-      A performance tip for tuning zero copy in VM2NIC case is to adjust the
-      frequency of mbuf free (i.e. adjust tx_free_threshold of i40e driver) to
-      balance consumer and producer.
-
-    * Guest memory should be backended with huge pages to achieve better
-      performance. Using 1G page size is the best.
-
-      When dequeue zero copy is enabled, the guest phys address and host phys
-      address mapping has to be established. Using non-huge pages means far
-      more page segments. To make it simple, DPDK vhost does a linear search
-      of those segments, thus the fewer the segments, the quicker we will get
-      the mapping. NOTE: we may speed it by using tree searching in future.
-
-    * zero copy can not work when using vfio-pci with iommu mode currently, this
-      is because we don't setup iommu dma mapping for guest memory. If you have
-      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
   - ``RTE_VHOST_USER_IOMMU_SUPPORT``
 
     IOMMU support will be enabled when this flag is set. It is disabled by


@@ -289,11 +245,13 @@ The following is an overview of some key Vhost API functions:
 
   Unregister the async copy device channel from a vhost queue.
 
 
   Unregister the async copy device channel from a vhost queue.
 

-* ``rte_vhost_submit_enqueue_burst(vid, queue_id, pkts, count)``
+* ``rte_vhost_submit_enqueue_burst(vid, queue_id, pkts, count, comp_pkts, comp_count)``

 
   Submit an enqueue request to transmit ``count`` packets from host to guest
 
   Submit an enqueue request to transmit ``count`` packets from host to guest

-  by async data path. Enqueue is not guaranteed to finish upon the return of
-  this API call.
+  by async data path. Successfully enqueued packets can be transfer completed
+  or being occupied by DMA engines; transfer completed packets are returned in
+  ``comp_pkts``, but others are not guaranteed to finish, when this API
+  call returns.

 
   Applications must not free the packets submitted for enqueue until the
   packets are completed.
 
   Applications must not free the packets submitted for enqueue until the
   packets are completed.


@@ -362,16 +320,16 @@ Guest memory requirement
 
 * Memory pre-allocation
 
 
 * Memory pre-allocation
 

-  For non-zerocopy non-async data path, guest memory pre-allocation is not a
+  For non-async data path, guest memory pre-allocation is not a

   must. This can help save of memory. If users really want the guest memory
   to be pre-allocated (e.g., for performance reason), we can add option
   ``-mem-prealloc`` when starting QEMU. Or, we can lock all memory at vhost
   side which will force memory to be allocated when mmap at vhost side;
   option --mlockall in ovs-dpdk is an example in hand.
 
   must. This can help save of memory. If users really want the guest memory
   to be pre-allocated (e.g., for performance reason), we can add option
   ``-mem-prealloc`` when starting QEMU. Or, we can lock all memory at vhost
   side which will force memory to be allocated when mmap at vhost side;
   option --mlockall in ovs-dpdk is an example in hand.
 

-  For async and zerocopy data path, we force the VM memory to be
-  pre-allocated at vhost lib when mapping the guest memory; and also we need
-  to lock the memory to prevent pages being swapped out to disk.
+  For async data path, we force the VM memory to be pre-allocated at vhost
+  lib when mapping the guest memory; and also we need to lock the memory to
+  prevent pages being swapped out to disk.

 
 * Memory sharing
 
 
 * Memory sharing