Hi Viacheslav, On Wed, Dec 11, 2019 at 05:01:33PM +0000, Viacheslav Ovsiienko wrote: > Some PMDs inline the mbuf data buffer directly to device transmit descriptor. > This is in order to save the overhead of the PCI headers imposed when the > device DMA reads the data by buffer pointer. For some devices it is essential > in order to provide the full bandwidth. > > However, there are cases where such inlining is in-efficient. For example, > when > the data buffer resides on other device memory (like GPU or storage device). > Attempt to inline such buffer will result in high PCI overhead for reading > and copying the data from the remote device to the host memory. > > To support a mixed traffic pattern (some buffers from local host memory, some > buffers from other devices) with high bandwidth, a hint flag is introduced in > the mbuf. > > Application will hint the PMD whether or not it should try to inline the > given mbuf data buffer. PMD should do the best effort to act upon this > request. > > The hint flag RTE_NET_MLX5_DYNFLAG_NO_INLINE_NAME is supposed to be dynamic, > registered by application with rte_mbuf_dynflag_register(). This flag is > purely vendor specific and declared in PMD specific header rte_pmd_mlx5.h, > which is intended to be used by specific application. > > To query the supported specific flags in runtime the private routine is > introduced: > > int rte_pmd_mlx5_get_dyn_flag_names( > uint16_t port, > char *names[], > uint16_t n) > > It returns the array of currently (over present hardware and configuration) > supported specific flags. > > The "not inline hint" feature operating flow is the following one: > - application start > - probe the devices, ports are created > - query the port capabilities > - if port supporting the feature is found > - register dynamic flag RTE_NET_MLX5_DYNFLAG_NO_INLINE_NAME > - application starts the ports > - on dev_start() PMD checks whether the feature flag is registered and > enables the feature support in datapath > - application might set this flag in ol_flags field of mbuf in the packets > being sent and PMD will handle ones appropriately. > > Signed-off-by: Shahaf Shuler <shah...@mellanox.com> > Signed-off-by: Viacheslav Ovsiienko <viachesl...@mellanox.com> > > --- > v1: https://patches.dpdk.org/patch/61348/ >
It looks the patch is missing. I think a dynamic flag is the good solution for this problem: the pmd can send a pmd-specific hint to the application, without impacting the way it works today. Olivier
