551ace124d
Profiling has shown that sdma_lock is proving a bottleneck for performance. The situations include: - RDMA reads when krcvqs > 1 - post sends from multiple threads For RDMA read the current global qib_wq mechanism runs on all CPUs and contends for the sdma_lock when multiple RMDA read requests are fielded on differenct CPUs. For post sends, the direct call to qib_do_send() from multiple threads causes the contention. Since the sdma mechanism is per port, this fix converts the existing workqueue to a per port single thread workqueue to reduce the lock contention in the RDMA read case, and for any other case where the QP is scheduled via the workqueue mechanism from more than 1 CPU. For the post send case, This patch modifies the post send code to test for a non empty sdma engine. If the sdma is not idle the (now single thread) workqueue will be used to trigger the send engine instead of the direct call to qib_do_send(). Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com> Signed-off-by: Roland Dreier <roland@purestorage.com> |
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