• Sebastian Sanchez's avatar
    IB/{hfi1, rdmavt, qib}: Implement CQ completion vector support · 5d18ee67
    Sebastian Sanchez authored
    Currently the driver doesn't support completion vectors. These
    are used to indicate which sets of CQs should be grouped together
    into the same vector. A vector is a CQ processing thread that
    runs on a specific CPU.
    If an application has several CQs bound to different completion
    vectors, and each completion vector runs on different CPUs, then
    the completion queue workload is balanced. This helps scale as more
    nodes are used.
    Implement CQ completion vector support using a global workqueue
    where a CQ entry is queued to the CPU corresponding to the CQ's
    completion vector. Since the workqueue is global, it's guaranteed
    to always be there when queueing CQ entries; Therefore, the RCU
    locking for cq->rdi->worker in the hot path is superfluous.
    Each completion vector is assigned to a different CPU. The number of
    completion vectors available is computed by taking the number of
    online, physical CPUs from the local NUMA node and subtracting the
    CPUs used for kernel receive queues and the general interrupt.
    Special use cases:
      * If there are no CPUs left for completion vectors, the same CPU
        for the general interrupt is used; Therefore, there would only
        be one completion vector available.
      * For multi-HFI systems, the number of completion vectors available
        for each device is the total number of completion vectors in
        the local NUMA node divided by the number of devices in the same
        NUMA node. If there's a division remainder, the first device to
        get initialized gets an extra completion vector.
    Upon a CQ creation, an invalid completion vector could be specified.
    Handle it as follows:
      * If the completion vector is less than 0, set it to 0.
      * Set the completion vector to the result of the passed completion
        vector moded with the number of device completion vectors
    Reviewed-by: default avatarMike Marciniszyn <mike.marciniszyn@intel.com>
    Signed-off-by: default avatarSebastian Sanchez <sebastian.sanchez@intel.com>
    Signed-off-by: default avatarDennis Dalessandro <dennis.dalessandro@intel.com>
    Signed-off-by: default avatarDoug Ledford <dledford@redhat.com>
rdmavt_cq.h 3.4 KB