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Date:      Wed, 13 May 2015 10:18:45 +0000 (UTC)
From:      Alexander Motin <mav@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-10@freebsd.org
Subject:   svn commit: r282839 - stable/10/usr.sbin/bhyve
Message-ID:  <201505131018.t4DAIjE8086320@svn.freebsd.org>
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Author: mav
Date: Wed May 13 10:18:44 2015
New Revision: 282839
URL: https://svnweb.freebsd.org/changeset/base/282839

Log:
  MFC r281764, r282563: Disable RX/TX queues notifications when not needed.
  
  This reduces CPU load and doubles iperf throughput, reaching 2-3Gbit/s.
  
  Sponsored by:	iXsystems, Inc.

Modified:
  stable/10/usr.sbin/bhyve/pci_virtio_net.c
Directory Properties:
  stable/10/   (props changed)

Modified: stable/10/usr.sbin/bhyve/pci_virtio_net.c
==============================================================================
--- stable/10/usr.sbin/bhyve/pci_virtio_net.c	Wed May 13 10:17:34 2015	(r282838)
+++ stable/10/usr.sbin/bhyve/pci_virtio_net.c	Wed May 13 10:18:44 2015	(r282839)
@@ -34,6 +34,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/select.h>
 #include <sys/uio.h>
 #include <sys/ioctl.h>
+#include <machine/atomic.h>
 #include <net/ethernet.h>
 
 #include <errno.h>
@@ -393,6 +394,7 @@ pci_vtnet_ping_rxq(void *vsc, struct vqu
 	 */
 	if (sc->vsc_rx_ready == 0) {
 		sc->vsc_rx_ready = 1;
+		vq->vq_used->vu_flags |= VRING_USED_F_NO_NOTIFY;
 	}
 }
 
@@ -438,6 +440,7 @@ pci_vtnet_ping_txq(void *vsc, struct vqu
 
 	/* Signal the tx thread for processing */
 	pthread_mutex_lock(&sc->tx_mtx);
+	vq->vq_used->vu_flags |= VRING_USED_F_NO_NOTIFY;
 	if (sc->tx_in_progress == 0)
 		pthread_cond_signal(&sc->tx_cond);
 	pthread_mutex_unlock(&sc->tx_mtx);
@@ -451,7 +454,7 @@ pci_vtnet_tx_thread(void *param)
 {
 	struct pci_vtnet_softc *sc = param;
 	struct vqueue_info *vq;
-	int have_work, error;
+	int error;
 
 	vq = &sc->vsc_queues[VTNET_TXQ];
 
@@ -465,19 +468,17 @@ pci_vtnet_tx_thread(void *param)
 
 	for (;;) {
 		/* note - tx mutex is locked here */
-		do {
-			if (sc->resetting)
-				have_work = 0;
-			else
-				have_work = vq_has_descs(vq);
-
-			if (!have_work) {
-				sc->tx_in_progress = 0;
-				error = pthread_cond_wait(&sc->tx_cond,
-							  &sc->tx_mtx);
-				assert(error == 0);
-			}
-		} while (!have_work);
+		while (sc->resetting || !vq_has_descs(vq)) {
+			vq->vq_used->vu_flags &= ~VRING_USED_F_NO_NOTIFY;
+			mb();
+			if (!sc->resetting && vq_has_descs(vq))
+				break;
+
+			sc->tx_in_progress = 0;
+			error = pthread_cond_wait(&sc->tx_cond, &sc->tx_mtx);
+			assert(error == 0);
+		}
+		vq->vq_used->vu_flags |= VRING_USED_F_NO_NOTIFY;
 		sc->tx_in_progress = 1;
 		pthread_mutex_unlock(&sc->tx_mtx);

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