• Chuck Lever's avatar
    svcrdma: Avoid DMA mapping small RPC Replies · 0dabe948
    Chuck Lever authored
    On some platforms, DMA mapping part of a page is more costly than
    copying bytes. Indeed, not involving the I/O MMU can help the
    RPC/RDMA transport scale better for tiny I/Os across more RDMA
    devices. This is because interaction with the I/O MMU is eliminated
    for each of these small I/Os. Without the explicit unmapping, the
    NIC no longer needs to do a costly internal TLB shoot down for
    buffers that are just a handful of bytes.
    
    Since pull-up is now a more a frequent operation, I've introduced a
    trace point in the pull-up path. It can be used for debugging or
    user-space tools that count pull-up frequency.
    Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
    0dabe948
svc_rdma_sendto.c 27.8 KB