IB/rdmavt: Fracture single lock used for posting and processing RWQEs

Usage of single lock prevents fetching posted and processing receive work
queue entries from progressing simultaneously and impacts overall
performance.

Fracture the single lock used for posting and processing Receive Work
Queue Entries (RWQEs) to allow the circular buffer to be filled and
emptied at the same time. Two new spinlocks - one for the producers and
one for the consumers used for posting and processing RWQEs simultaneously
and the two indices are define on two different cache lines. The threshold
count is used to avoid reading other index in different cache line every
time.

Signed-off-by: Harish Chegondi <harish.chegondi@intel.com>
Signed-off-by: Kamenee Arumugam <kamenee.arumugam@intel.com>
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/include/rdma/rdmavt_qp.h b/include/rdma/rdmavt_qp.h
index ee55fd04f6da..de5915b244be 100644
--- a/include/rdma/rdmavt_qp.h
+++ b/include/rdma/rdmavt_qp.h
@@ -180,7 +180,9 @@ struct rvt_swqe {
 
 /**
  * struct rvt_krwq - kernel struct receive work request
+ * @p_lock: lock to protect producer of the kernel buffer
  * @head: index of next entry to fill
+ * @c_lock:lock to protect consumer of the kernel buffer
  * @tail: index of next entry to pull
  * @count: count is aproximate of total receive enteries posted
  * @rvt_rwqe: struct of receive work request queue entry
@@ -190,8 +192,13 @@ struct rvt_swqe {
  * mode user.
  */
 struct rvt_krwq {
+	spinlock_t p_lock;	/* protect producer */
 	u32 head;               /* new work requests posted to the head */
+
+	/* protect consumer */
+	spinlock_t c_lock ____cacheline_aligned_in_smp;
 	u32 tail;               /* receives pull requests from here. */
+	u32 count;		/* approx count of receive entries posted */
 	struct rvt_rwqe *curr_wq;
 	struct rvt_rwqe wq[];
 };