svn commit: r264348 - head/sys/dev/iscsi

[Alexander Motin]

Author: mav
Date: Fri Apr 11 18:26:08 2014
New Revision: 264348
URL: http://svnweb.freebsd.org/changeset/base/264348

Log:
  Improve use of socket buffer upcalls.
  
  Use soreadable()/sowriteable() in socket upcalls to avoid extra wakeups
  until we have enough data to read or space to write.
  
  Increase partial receive len from 1K to 128K to not wake up on every
  received packet.
  
  This significantly reduces locks congestion and CPU usage and improves
  throughput for large I/Os on NICs without TSO and LRO.
  
  Reviewed by:	trasz
  Sponsored by:	iXsystems, Inc.

Modified:
  head/sys/dev/iscsi/icl.c

Modified: head/sys/dev/iscsi/icl.c
==============================================================================
--- head/sys/dev/iscsi/icl.c	Fri Apr 11 18:19:21 2014	(r264347)
+++ head/sys/dev/iscsi/icl.c	Fri Apr 11 18:26:08 2014	(r264348)
@@ -45,6 +45,7 @@
 #include <sys/mbuf.h>
 #include <sys/mutex.h>
 #include <sys/module.h>
+#include <sys/protosw.h>
 #include <sys/socket.h>
 #include <sys/socketvar.h>
 #include <sys/sysctl.h>
@@ -67,7 +68,7 @@ static int coalesce = 1;
 TUNABLE_INT("kern.icl.coalesce", &coalesce);
 SYSCTL_INT(_kern_icl, OID_AUTO, coalesce, CTLFLAG_RWTUN,
     &coalesce, 1, "Try to coalesce PDUs before sending");
-static int partial_receive_len = 1 * 1024; /* XXX: More? */
+static int partial_receive_len = 128 * 1024;
 TUNABLE_INT("kern.icl.partial_receive_len", &partial_receive_len);
 SYSCTL_INT(_kern_icl, OID_AUTO, partial_receive_len, CTLFLAG_RWTUN,
     &partial_receive_len, 1 * 1024, "Minimum read size for partially received "
@@ -750,12 +751,19 @@ icl_receive_thread(void *arg)
 			break;
 		}
 
+		/*
+		 * Set the low watermark, to be checked by
+		 * soreadable() in icl_soupcall_receive()
+		 * to avoid unneccessary wakeups until there
+		 * is enough data received to read the PDU.
+		 */
 		SOCKBUF_LOCK(&so->so_rcv);
 		available = so->so_rcv.sb_cc;
 		if (available < ic->ic_receive_len) {
 			so->so_rcv.sb_lowat = ic->ic_receive_len;
 			cv_wait(&ic->ic_receive_cv, &so->so_rcv.sb_mtx);
-		}
+		} else
+			so->so_rcv.sb_lowat = so->so_rcv.sb_hiwat + 1;
 		SOCKBUF_UNLOCK(&so->so_rcv);
 
 		icl_conn_receive_pdus(ic, available);
@@ -772,6 +780,9 @@ icl_soupcall_receive(struct socket *so, 
 {
 	struct icl_conn *ic;
 
+	if (!soreadable(so))
+		return (SU_OK);
+
 	ic = arg;
 	cv_signal(&ic->ic_receive_cv);
 	return (SU_OK);
@@ -854,10 +865,10 @@ icl_conn_send_pdus(struct icl_conn *ic, 
 	available = sbspace(&so->so_snd);
 
 	/*
-	 * Notify the socket layer that it doesn't need to call
-	 * send socket upcall for the time being.
+	 * Notify the socket upcall that we don't need wakeups
+	 * for the time being.
 	 */
-	so->so_snd.sb_lowat = so->so_snd.sb_hiwat;
+	so->so_snd.sb_lowat = so->so_snd.sb_hiwat + 1;
 	SOCKBUF_UNLOCK(&so->so_snd);
 
 	while (!STAILQ_EMPTY(queue)) {
@@ -873,7 +884,8 @@ icl_conn_send_pdus(struct icl_conn *ic, 
 #endif
 
 			/*
-			 * Set the low watermark on the socket,
+			 * Set the low watermark, to be checked by
+			 * sowritable() in icl_soupcall_send()
 			 * to avoid unneccessary wakeups until there
 			 * is enough space for the PDU to fit.
 			 */
@@ -1016,6 +1028,9 @@ icl_soupcall_send(struct socket *so, voi
 {
 	struct icl_conn *ic;
 
+	if (!sowriteable(so))
+		return (SU_OK);
+
 	ic = arg;
 
 	ICL_CONN_LOCK(ic);