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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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0ca77dc372
Because internal memory registration is an expensive and synchronous operation, xprtrdma pre-registers send and receive buffers at mount time, and then re-uses them for each RPC. A "hardway" allocation is a memory allocation and registration that replaces a send buffer during the processing of an RPC. Hardway must be done if the RPC send buffer is too small to accommodate an RPC's call and reply headers. For xprtrdma, each RPC send buffer is currently part of struct rpcrdma_req so that xprt_rdma_free(), which is passed nothing but the address of an RPC send buffer, can find its matching struct rpcrdma_req and rpcrdma_rep quickly via container_of / offsetof. That means that hardway currently has to replace a whole rpcrmda_req when it replaces an RPC send buffer. This is often a fairly hefty chunk of contiguous memory due to the size of the rl_segments array and the fact that both the send and receive buffers are part of struct rpcrdma_req. Some obscure re-use of fields in rpcrdma_req is done so that xprt_rdma_free() can detect replaced rpcrdma_req structs, and restore the original. This commit breaks apart the RPC send buffer and struct rpcrdma_req so that increasing the size of the rl_segments array does not change the alignment of each RPC send buffer. (Increasing rl_segments is needed to bump up the maximum r/wsize for NFS/RDMA). This change opens up some interesting possibilities for improving the design of xprt_rdma_allocate(). xprt_rdma_allocate() is now the one place where RPC send buffers are allocated or re-allocated, and they are now always left in place by xprt_rdma_free(). A large re-allocation that includes both the rl_segments array and the RPC send buffer is no longer needed. Send buffer re-allocation becomes quite rare. Good send buffer alignment is guaranteed no matter what the size of the rl_segments array is. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Reviewed-by: Steve Wise <swise@opengridcomputing.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com> |
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