From: "Xia, Chenbo" <chenbo.xia@intel.com>
To: "Fu, Patrick" <patrick.fu@intel.com>,
"dev@dpdk.org" <dev@dpdk.org>,
"maxime.coquelin@redhat.com" <maxime.coquelin@redhat.com>
Subject: Re: [dpdk-dev] [PATCH v1 1/2] doc: update guides for vhost async APIs
Date: Wed, 22 Jul 2020 11:21:27 +0000 [thread overview]
Message-ID: <MN2PR11MB406305F1F8A75DFA46A3F3C79C790@MN2PR11MB4063.namprd11.prod.outlook.com> (raw)
In-Reply-To: <20200722105741.3421255-2-patrick.fu@intel.com>
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
next prev parent reply other threads:[~2020-07-22 11:21 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-22 10:57 [dpdk-dev] [PATCH v1 0/2] update docs for vhost async API patrick.fu
2020-07-22 10:57 ` [dpdk-dev] [PATCH v1 1/2] doc: update guides for vhost async APIs patrick.fu
2020-07-22 11:21 ` Xia, Chenbo [this message]
2020-07-22 15:06 ` Fu, Patrick
2020-07-22 10:57 ` [dpdk-dev] [PATCH v1 2/2] doc: update release notes " patrick.fu
2020-07-22 11:25 ` Xia, Chenbo
2020-07-22 15:07 ` Fu, Patrick
2020-07-22 15:01 ` [dpdk-dev] [PATCH v2 0/2] update docs " patrick.fu
2020-07-22 15:01 ` [dpdk-dev] [PATCH v2 1/2] doc: update guides " patrick.fu
2020-07-25 6:58 ` Xia, Chenbo
2020-07-28 9:01 ` Maxime Coquelin
2020-07-22 15:01 ` [dpdk-dev] [PATCH v2 2/2] doc: update release notes " patrick.fu
2020-07-25 6:59 ` Xia, Chenbo
2020-07-28 9:06 ` Maxime Coquelin
2020-07-28 15:26 ` [dpdk-dev] [PATCH v2 0/2] update docs " Maxime Coquelin
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