guest->host throughput with 04-no-tx-timer

guest->host host->guest || cpu utilization throughput vmexits || 01-tx-notifies-disabled-for-longer 02-flush-in-io-thread 03-catch-more-io 04-no-tx-timer 05-drop-mutex

From: Mark McLoughlin 
Subject: [PATCH] kvm: qemu: virtio_net: remove the tx timer

Signed-off-by: Mark McLoughlin 
---
 qemu/hw/virtio-net.c |   42 +++---------------------------------------
 1 files changed, 3 insertions(+), 39 deletions(-)

diff --git a/qemu/hw/virtio-net.c b/qemu/hw/virtio-net.c
index 32a93ba..8a7efd9 100644
--- a/qemu/hw/virtio-net.c
+++ b/qemu/hw/virtio-net.c
@@ -35,8 +35,6 @@
 #define VIRTIO_NET_F_HOST_ECN	13	/* Host can handle TSO[6] w/ ECN in. */
 #define VIRTIO_NET_F_HOST_UFO	14	/* Host can handle UFO in. */
 
-#define TX_TIMER_INTERVAL 150000 /* 150 us */
-
 /* The config defining mac address (6 bytes) */
 struct virtio_net_config
 {
@@ -68,8 +66,6 @@ typedef struct VirtIONet
     VirtQueue *rx_vq;
     VirtQueue *tx_vq;
     VLANClientState *vc;
-    QEMUTimer *tx_timer;
-    int tx_timer_active;
     QEMUBH *tx_bh;
     int tx_bh_scheduled;
 } VirtIONet;
@@ -278,30 +274,9 @@ static void virtio_net_handle_tx(VirtIODevice *vdev, VirtQueue *vq)
     if (n->tx_bh_scheduled)
 	return;
 
-    if (n->tx_timer_active) {
-	qemu_del_timer(n->tx_timer);
-	n->tx_timer_active = 0;
-	qemu_bh_schedule(n->tx_bh);
-	n->tx_bh_scheduled = 1;
-    } else {
-	qemu_mod_timer(n->tx_timer,
-		       qemu_get_clock(vm_clock) + TX_TIMER_INTERVAL);
-	n->tx_timer_active = 1;
-	vq->vring.used->flags |= VRING_USED_F_NO_NOTIFY;
-    }
-}
-
-static void virtio_net_tx_timer(void *opaque)
-{
-    VirtIONet *n = opaque;
-
-    n->tx_timer_active = 0;
-
-    if (virtio_net_flush_tx(n, n->tx_vq, 1)) {
-	n->tx_vq->vring.used->flags |= VRING_USED_F_NO_NOTIFY;
-	qemu_bh_schedule(n->tx_bh);
-	n->tx_bh_scheduled = 1;
-    }
+    vq->vring.used->flags |= VRING_USED_F_NO_NOTIFY;
+    qemu_bh_schedule(n->tx_bh);
+    n->tx_bh_scheduled = 1;
 }
 
 static void virtio_net_tx_bh(void *opaque)
@@ -324,7 +299,6 @@ static void virtio_net_save(QEMUFile *f, void *opaque)
     virtio_save(&n->vdev, f);
 
     qemu_put_buffer(f, n->mac, 6);
-    qemu_put_be32(f, n->tx_timer_active);
 }
 
 static int virtio_net_load(QEMUFile *f, void *opaque, int version_id)
@@ -337,12 +311,6 @@ static int virtio_net_load(QEMUFile *f, void *opaque, int version_id)
     virtio_load(&n->vdev, f);
 
     qemu_get_buffer(f, n->mac, 6);
-    n->tx_timer_active = qemu_get_be32(f);
-
-    if (n->tx_timer_active) {
-	qemu_mod_timer(n->tx_timer,
-		       qemu_get_clock(vm_clock) + TX_TIMER_INTERVAL);
-    }
 
     return 0;
 }
@@ -351,8 +319,6 @@ static int virtio_net_uninit(PCIDevice *dev)
 {
     VirtIONet *n = (VirtIONet *)dev;
 
-    qemu_del_timer(n->tx_timer);
-    qemu_free_timer(n->tx_timer);
     qemu_bh_delete(n->tx_bh);
 
     return 0;
@@ -379,8 +345,6 @@ PCIDevice *virtio_net_init(PCIBus *bus, NICInfo *nd, int devfn)
     n->vc = qemu_new_vlan_client(nd->vlan, virtio_net_receive,
                                  virtio_net_can_receive, n);
 
-    n->tx_timer = qemu_new_timer(vm_clock, virtio_net_tx_timer, n);
-    n->tx_timer_active = 0;
     n->tx_bh = qemu_bh_new(virtio_net_tx_bh, n);
     n->tx_bh_scheduled = 0;
 
-- 
1.6.0.1