Current async ops allows check_completed_copies() callback to return
arbitrary number of async iov segments finished from backend async
devices. This design creates complexity for vhost to handle breaking
transfer of a single packet (i.e. transfer completes in the middle
of a async descriptor) and prevents application callbacks from
leveraging hardware capability to offload the work. Thus, this patch
enforces the check_completed_copies() callback to return the number
of async memory descriptors, which is aligned with async transfer
data ops callbacks. vhost async data path are revised to work with
new ops define, which provides a clean and simplified processing.
Signed-off-by: Patrick Fu <patrick.fu@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
The async copy device callbacks are used by async APIs to transfer data
and check completion status. Async APIs return the number of packets
successfully processed to the caller applications and no error
(negative) value is allowed for API return value. Thus, negative return
values from async device callbacks don't have meaningful usage, while
adding overhead in checking the return value validity. This patch change
the callback return values from "int" to "uint32_t" to get aligned with
async API definition.
Fixes: 78639d54563a ("vhost: introduce async enqueue registration API")
Signed-off-by: Patrick Fu <patrick.fu@intel.com>
Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
This patch implements async enqueue data path for split ring. 2 new
async data path APIs are defined, by which applications can submit
and poll packets to/from async engines. The async engine is either
a physical DMA device or it could also be a software emulated backend.
The async enqueue data path leverages callback functions registered by
applications to work with the async engine.
Signed-off-by: Patrick Fu <patrick.fu@intel.com>
Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>
Performing large memory copies usually takes up a major part of CPU
cycles and becomes the hot spot in vhost-user enqueue operation. To
offload the large copies from CPU to the DMA devices, asynchronous
APIs are introduced, with which the CPU just submits copy jobs to
the DMA but without waiting for its copy completion. Thus, there is
no CPU intervention during data transfer. We can save precious CPU
cycles and improve the overall throughput for vhost-user based
applications. This patch introduces registration/un-registration
APIs for vhost async data enqueue operation. Together with the
registration APIs implementations, data structures and the prototype
of the async callback functions required for async enqueue data path
are also defined.
Signed-off-by: Patrick Fu <patrick.fu@intel.com>
Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>
