[v1,1/2] doc: update guides for vhost async APIs
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Commit Message
From: Patrick Fu <patrick.fu@intel.com>
Update vhost guides to document vhost async APIs
Signed-off-by: Patrick Fu <patrick.fu@intel.com>
---
doc/guides/prog_guide/vhost_lib.rst | 86 ++++++++++++++++++++++++++---
1 file changed, 77 insertions(+), 9 deletions(-)
Comments
Hi Patrick,
> -----Original Message-----
> From: Fu, Patrick <patrick.fu@intel.com>
> Sent: Wednesday, July 22, 2020 6:58 PM
> To: dev@dpdk.org; maxime.coquelin@redhat.com; Xia, Chenbo
> <chenbo.xia@intel.com>
> Cc: Fu, Patrick <patrick.fu@intel.com>
> Subject: [PATCH v1 1/2] doc: update guides for vhost async APIs
>
> From: Patrick Fu <patrick.fu@intel.com>
>
> Update vhost guides to document vhost async APIs
>
> Signed-off-by: Patrick Fu <patrick.fu@intel.com>
> ---
> doc/guides/prog_guide/vhost_lib.rst | 86 ++++++++++++++++++++++++++---
> 1 file changed, 77 insertions(+), 9 deletions(-)
>
> diff --git a/doc/guides/prog_guide/vhost_lib.rst
> b/doc/guides/prog_guide/vhost_lib.rst
> index db921f922..cce8b6ae7 100644
> --- a/doc/guides/prog_guide/vhost_lib.rst
> +++ b/doc/guides/prog_guide/vhost_lib.rst
> @@ -147,6 +147,21 @@ The following is an overview of some key Vhost API
> functions:
>
> It is disabled by default.
>
> + - ``RTE_VHOST_USER_ASYNC_COPY``
> +
> + Asynchronous data path will be enabled when this flag is set. Async data
> + path allows applications to register async copy devices (typically
> + hardware DMA channels) to the vhost queues. Vhost leverages the copy
> + device registered to offload CPU from memory copy operations. A set of
You mean 'free' CPU from memory copy?
> + async data path APIs are defined for DPDK applications to make use of
> + the async capability. Only packets enqueued/dequeued by async APIs are
> + processed through the async data path.
> +
> + Currently this feature is only implemented on split ring enqueue data
> + path.
> +
> + It is disabled by default.
> +
> * ``rte_vhost_driver_set_features(path, features)``
>
> This function sets the feature bits the vhost-user driver supports. The @@ -
> 235,6 +250,59 @@ The following is an overview of some key Vhost API
> functions:
>
> Enable or disable zero copy feature of the vhost crypto backend.
>
> +* ``rte_vhost_async_channel_register(vid, queue_id, features, ops)``
> +
> + Register a vhost queue with async copy device channel.
> + Following device ``features`` must be specified together with the
> + registration:
> +
> + * ``async_inorder``
> +
> + Async copy device can guarantee the ordering of copy completion
> + sequence. Copies are completed in the same order with that at
> + the submission time.
> +
> + Currently, only ``async_inorder`` capable device is supported by vhost.
> +
> + * ``async_threshold``
> +
> + The copy length (in bytes) below which CPU copy will be used even if
> + applications call async vhost APIs to enqueue/dequeue data.
> +
> + Typical value is 512~1024 depending on the async device capability.
> +
> + Applications must provide following ``ops`` callbacks for vhost lib
> + to work with the async copye devices:
s/copye/copy
> +
> + * ``transfer_data(vid, queue_id, descs, opaque_data, count)``
> +
> + vhost invokes this function to submit copy data to the async devices.
> + For non-async_inorder capable devices, ``opaque_data`` could be used
> + for identifying the completed packets.
> +
> + * ``check_completed_copies(vid, queue_id, opaque_data, max_packets)``
> +
> + vhost invokes this function to get the copy data completed by async
> + devices.
> +
> +* ``rte_vhost_async_channel_unregister(vid, queue_id)``
> +
> + Unregister the async copy device from a vhost queue.
'Copy device channel' may be more accurate?
> +
> +* ``rte_vhost_submit_enqueue_burst(vid, queue_id, pkts, count)``
> +
> + 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.
> +
> + Applications must not free the packets submitted for enqueue until
> + the packets are completed.
> +
> +* ``rte_vhost_poll_enqueue_completed(vid, queue_id, pkts, count)``
> +
> + Poll enqueue completion status from async data path. Completed
> + packets are returned to applications through ``pkts``.
> +
> Vhost-user Implementations
> --------------------------
>
> @@ -294,16 +362,16 @@ Guest memory requirement
>
> * Memory pre-allocation
>
> - For non-zerocopy, 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.
> + For non-zerocopy 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.
>
> - For zerocopy, 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 or zerocopy, we force the VM memory to be
'For async or zerocopy data path' may be better?
Thanks!
Chenbo
> + 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
>
> --
> 2.18.4
Thanks for comments. v2 patch sent with all the changes suggested.
Thanks,
Patrick
> -----Original Message-----
> From: Xia, Chenbo <chenbo.xia@intel.com>
> Sent: Wednesday, July 22, 2020 7:21 PM
> To: Fu, Patrick <patrick.fu@intel.com>; dev@dpdk.org;
> maxime.coquelin@redhat.com
> Subject: RE: [PATCH v1 1/2] doc: update guides for vhost async APIs
>
> Hi Patrick,
>
> > -----Original Message-----
> > From: Fu, Patrick <patrick.fu@intel.com>
> > Sent: Wednesday, July 22, 2020 6:58 PM
> > To: dev@dpdk.org; maxime.coquelin@redhat.com; Xia, Chenbo
> > <chenbo.xia@intel.com>
> > Cc: Fu, Patrick <patrick.fu@intel.com>
> > Subject: [PATCH v1 1/2] doc: update guides for vhost async APIs
> >
> > From: Patrick Fu <patrick.fu@intel.com>
> >
> > Update vhost guides to document vhost async APIs
> >
> > Signed-off-by: Patrick Fu <patrick.fu@intel.com>
> > ---
> > doc/guides/prog_guide/vhost_lib.rst | 86
> > ++++++++++++++++++++++++++---
> > 1 file changed, 77 insertions(+), 9 deletions(-)
> >
> > diff --git a/doc/guides/prog_guide/vhost_lib.rst
> > b/doc/guides/prog_guide/vhost_lib.rst
> > index db921f922..cce8b6ae7 100644
> > --- a/doc/guides/prog_guide/vhost_lib.rst
> > +++ b/doc/guides/prog_guide/vhost_lib.rst
> > @@ -147,6 +147,21 @@ The following is an overview of some key Vhost
> > API
> > functions:
> >
> > It is disabled by default.
> >
> > + - ``RTE_VHOST_USER_ASYNC_COPY``
> > +
> > + Asynchronous data path will be enabled when this flag is set. Async
> data
> > + path allows applications to register async copy devices (typically
> > + hardware DMA channels) to the vhost queues. Vhost leverages the copy
> > + device registered to offload CPU from memory copy operations. A
> > + set of
>
> You mean 'free' CPU from memory copy?
>
> > + async data path APIs are defined for DPDK applications to make use of
> > + the async capability. Only packets enqueued/dequeued by async APIs
> are
> > + processed through the async data path.
> > +
> > + Currently this feature is only implemented on split ring enqueue data
> > + path.
> > +
> > + It is disabled by default.
> > +
> > * ``rte_vhost_driver_set_features(path, features)``
> >
> > This function sets the feature bits the vhost-user driver supports.
> > The @@ -
> > 235,6 +250,59 @@ The following is an overview of some key Vhost API
> > functions:
> >
> > Enable or disable zero copy feature of the vhost crypto backend.
> >
> > +* ``rte_vhost_async_channel_register(vid, queue_id, features, ops)``
> > +
> > + Register a vhost queue with async copy device channel.
> > + Following device ``features`` must be specified together with the
> > + registration:
> > +
> > + * ``async_inorder``
> > +
> > + Async copy device can guarantee the ordering of copy completion
> > + sequence. Copies are completed in the same order with that at
> > + the submission time.
> > +
> > + Currently, only ``async_inorder`` capable device is supported by vhost.
> > +
> > + * ``async_threshold``
> > +
> > + The copy length (in bytes) below which CPU copy will be used even if
> > + applications call async vhost APIs to enqueue/dequeue data.
> > +
> > + Typical value is 512~1024 depending on the async device capability.
> > +
> > + Applications must provide following ``ops`` callbacks for vhost lib
> > + to work with the async copye devices:
>
> s/copye/copy
>
> > +
> > + * ``transfer_data(vid, queue_id, descs, opaque_data, count)``
> > +
> > + vhost invokes this function to submit copy data to the async devices.
> > + For non-async_inorder capable devices, ``opaque_data`` could be used
> > + for identifying the completed packets.
> > +
> > + * ``check_completed_copies(vid, queue_id, opaque_data,
> > + max_packets)``
> > +
> > + vhost invokes this function to get the copy data completed by async
> > + devices.
> > +
> > +* ``rte_vhost_async_channel_unregister(vid, queue_id)``
> > +
> > + Unregister the async copy device from a vhost queue.
>
> 'Copy device channel' may be more accurate?
>
> > +
> > +* ``rte_vhost_submit_enqueue_burst(vid, queue_id, pkts, count)``
> > +
> > + 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.
> > +
> > + Applications must not free the packets submitted for enqueue until
> > + the packets are completed.
> > +
> > +* ``rte_vhost_poll_enqueue_completed(vid, queue_id, pkts, count)``
> > +
> > + Poll enqueue completion status from async data path. Completed
> > + packets are returned to applications through ``pkts``.
> > +
> > Vhost-user Implementations
> > --------------------------
> >
> > @@ -294,16 +362,16 @@ Guest memory requirement
> >
> > * Memory pre-allocation
> >
> > - For non-zerocopy, 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.
> > + For non-zerocopy 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.
> >
> > - For zerocopy, 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 or zerocopy, we force the VM memory to be
>
> 'For async or zerocopy data path' may be better?
>
> Thanks!
> Chenbo
>
> > + 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
> >
> > --
> > 2.18.4
@@ -147,6 +147,21 @@ The following is an overview of some key Vhost API functions:
It is disabled by default.
+ - ``RTE_VHOST_USER_ASYNC_COPY``
+
+ Asynchronous data path will be enabled when this flag is set. Async data
+ path allows applications to register async copy devices (typically
+ hardware DMA channels) to the vhost queues. Vhost leverages the copy
+ device registered to offload CPU from memory copy operations. A set of
+ async data path APIs are defined for DPDK applications to make use of
+ the async capability. Only packets enqueued/dequeued by async APIs are
+ processed through the async data path.
+
+ Currently this feature is only implemented on split ring enqueue data
+ path.
+
+ It is disabled by default.
+
* ``rte_vhost_driver_set_features(path, features)``
This function sets the feature bits the vhost-user driver supports. The
@@ -235,6 +250,59 @@ The following is an overview of some key Vhost API functions:
Enable or disable zero copy feature of the vhost crypto backend.
+* ``rte_vhost_async_channel_register(vid, queue_id, features, ops)``
+
+ Register a vhost queue with async copy device channel.
+ Following device ``features`` must be specified together with the
+ registration:
+
+ * ``async_inorder``
+
+ Async copy device can guarantee the ordering of copy completion
+ sequence. Copies are completed in the same order with that at
+ the submission time.
+
+ Currently, only ``async_inorder`` capable device is supported by vhost.
+
+ * ``async_threshold``
+
+ The copy length (in bytes) below which CPU copy will be used even if
+ applications call async vhost APIs to enqueue/dequeue data.
+
+ Typical value is 512~1024 depending on the async device capability.
+
+ Applications must provide following ``ops`` callbacks for vhost lib to
+ work with the async copye devices:
+
+ * ``transfer_data(vid, queue_id, descs, opaque_data, count)``
+
+ vhost invokes this function to submit copy data to the async devices.
+ For non-async_inorder capable devices, ``opaque_data`` could be used
+ for identifying the completed packets.
+
+ * ``check_completed_copies(vid, queue_id, opaque_data, max_packets)``
+
+ vhost invokes this function to get the copy data completed by async
+ devices.
+
+* ``rte_vhost_async_channel_unregister(vid, queue_id)``
+
+ Unregister the async copy device from a vhost queue.
+
+* ``rte_vhost_submit_enqueue_burst(vid, queue_id, pkts, count)``
+
+ 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.
+
+ Applications must not free the packets submitted for enqueue until the
+ packets are completed.
+
+* ``rte_vhost_poll_enqueue_completed(vid, queue_id, pkts, count)``
+
+ Poll enqueue completion status from async data path. Completed packets
+ are returned to applications through ``pkts``.
+
Vhost-user Implementations
--------------------------
@@ -294,16 +362,16 @@ Guest memory requirement
* Memory pre-allocation
- For non-zerocopy, 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.
+ For non-zerocopy 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.
- For zerocopy, 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 or zerocopy, 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