RDS: add receive message trace used by application

Socket option to tap receive path latency in various stages
in nano seconds. It can be enabled on selective sockets using
using SO_RDS_MSG_RXPATH_LATENCY socket option. RDS will return
the data to application with RDS_CMSG_RXPATH_LATENCY in defined
format. Scope is left to add more trace points for future
without need of change in the interface.

Reviewed-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/include/uapi/linux/rds.h b/include/uapi/linux/rds.h
index 0f9265cb2a96..3833113ab2c0 100644
--- a/include/uapi/linux/rds.h
+++ b/include/uapi/linux/rds.h
@@ -52,6 +52,13 @@
 #define RDS_GET_MR_FOR_DEST		7
 #define SO_RDS_TRANSPORT		8
 
+/* Socket option to tap receive path latency
+ *	SO_RDS: SO_RDS_MSG_RXPATH_LATENCY
+ *	Format used struct rds_rx_trace_so
+ */
+#define SO_RDS_MSG_RXPATH_LATENCY	10
+
+
 /* supported values for SO_RDS_TRANSPORT */
 #define	RDS_TRANS_IB	0
 #define	RDS_TRANS_IWARP	1
@@ -77,6 +84,12 @@
  *	the same as for the GET_MR setsockopt.
  * RDS_CMSG_RDMA_STATUS (recvmsg)
  *	Returns the status of a completed RDMA operation.
+ * RDS_CMSG_RXPATH_LATENCY(recvmsg)
+ *	Returns rds message latencies in various stages of receive
+ *	path in nS. Its set per socket using SO_RDS_MSG_RXPATH_LATENCY
+ *	socket option. Legitimate points are defined in
+ *	enum rds_message_rxpath_latency. More points can be added in
+ *	future. CSMG format is struct rds_cmsg_rx_trace.
  */
 #define RDS_CMSG_RDMA_ARGS		1
 #define RDS_CMSG_RDMA_DEST		2
@@ -87,6 +100,7 @@
 #define RDS_CMSG_ATOMIC_CSWP		7
 #define RDS_CMSG_MASKED_ATOMIC_FADD	8
 #define RDS_CMSG_MASKED_ATOMIC_CSWP	9
+#define RDS_CMSG_RXPATH_LATENCY		11
 
 #define RDS_INFO_FIRST			10000
 #define RDS_INFO_COUNTERS		10000
@@ -171,6 +185,25 @@ struct rds_info_rdma_connection {
 	uint32_t	rdma_mr_size;
 };
 
+/* RDS message Receive Path Latency points */
+enum rds_message_rxpath_latency {
+	RDS_MSG_RX_HDR_TO_DGRAM_START = 0,
+	RDS_MSG_RX_DGRAM_REASSEMBLE,
+	RDS_MSG_RX_DGRAM_DELIVERED,
+	RDS_MSG_RX_DGRAM_TRACE_MAX
+};
+
+struct rds_rx_trace_so {
+	u8 rx_traces;
+	u8 rx_trace_pos[RDS_MSG_RX_DGRAM_TRACE_MAX];
+};
+
+struct rds_cmsg_rx_trace {
+	u8 rx_traces;
+	u8 rx_trace_pos[RDS_MSG_RX_DGRAM_TRACE_MAX];
+	u64 rx_trace[RDS_MSG_RX_DGRAM_TRACE_MAX];
+};
+
 /*
  * Congestion monitoring.
  * Congestion control in RDS happens at the host connection