Currently if VIRTIO_RING_F_INDIRECT_DESC is enabled we will use indirect
descriptors even if we have plenty of space in the ring. This means that
we take a performance hit at all times due to the overhead of creating
indirect descriptors.
Instead, use it only after we're below a configurable offset.
Signed-off-by: Sasha Levin <levinsasha...@gmail.com>
---
drivers/block/virtio_blk.c | 4 ++++
drivers/char/hw_random/virtio-rng.c | 4 ++++
drivers/char/virtio_console.c | 4 ++++
drivers/net/virtio_net.c | 4 ++++
drivers/virtio/virtio_balloon.c | 4 ++++
drivers/virtio/virtio_ring.c | 21 +++++++++++++++------
include/linux/virtio.h | 1 +
net/9p/trans_virtio.c | 4 ++++
8 files changed, 40 insertions(+), 6 deletions(-)
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 693187d..a2c8d97 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -19,6 +19,9 @@ static DEFINE_IDA(vd_index_ida);
struct workqueue_struct *virtblk_wq;
+static unsigned int indirect_thresh = 0;
+module_param(indirect_thresh, uint, S_IRUGO);
+
struct virtio_blk
{
spinlock_t lock;
@@ -438,6 +441,7 @@ static int __devinit virtblk_probe(struct virtio_device
*vdev)
mutex_init(&vblk->config_lock);
INIT_WORK(&vblk->config_work, virtblk_config_changed_work);
vblk->config_enable = true;
+ vdev->indirect_thresh = indirect_thresh;
err = init_vq(vblk);
if (err)
diff --git a/drivers/char/hw_random/virtio-rng.c
b/drivers/char/hw_random/virtio-rng.c
index 723725b..bcaddb9 100644
--- a/drivers/char/hw_random/virtio-rng.c
+++ b/drivers/char/hw_random/virtio-rng.c
@@ -25,6 +25,9 @@
#include <linux/virtio_rng.h>
#include <linux/module.h>
+static unsigned int indirect_thresh = 0;
+module_param(indirect_thresh, uint, S_IRUGO);
+
static struct virtqueue *vq;
static unsigned int data_avail;
static DECLARE_COMPLETION(have_data);
@@ -90,6 +93,7 @@ static int virtrng_probe(struct virtio_device *vdev)
int err;
/* We expect a single virtqueue. */
+ vdev->indirect_thresh = indirect_thresh;
vq = virtio_find_single_vq(vdev, random_recv_done, "input");
if (IS_ERR(vq))
return PTR_ERR(vq);
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index cdf2f54..60397a4 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -37,6 +37,9 @@
#include <linux/module.h>
#include "../tty/hvc/hvc_console.h"
+static unsigned int indirect_thresh = 0;
+module_param(indirect_thresh, uint, S_IRUGO);
+
/*
* This is a global struct for storing common data for all the devices
* this driver handles.
@@ -1729,6 +1732,7 @@ static int __devinit virtcons_probe(struct virtio_device
*vdev)
max_nr_ports),
&portdev->config.max_nr_ports) == 0)
multiport = true;
+ vdev->indirect_thresh = indirect_thresh;
err = init_vqs(portdev);
if (err < 0) {
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index f18149a..5c1be92 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -34,6 +34,9 @@ static bool csum = true, gso = true;
module_param(csum, bool, 0444);
module_param(gso, bool, 0444);
+static unsigned int indirect_thresh = 0;
+module_param(indirect_thresh, uint, S_IRUGO);
+
/* FIXME: MTU in config. */
#define MAX_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
#define GOOD_COPY_LEN 128
@@ -1128,6 +1131,7 @@ static int virtnet_probe(struct virtio_device *vdev)
if (virtio_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF))
vi->mergeable_rx_bufs = true;
+ vdev->indirect_thresh = indirect_thresh;
err = init_vqs(vi);
if (err)
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index bfbc15c..4fc11ba 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -35,6 +35,9 @@
*/
#define VIRTIO_BALLOON_PAGES_PER_PAGE (PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
+static unsigned int indirect_thresh = 0;
+module_param(indirect_thresh, uint, S_IRUGO);
+
struct virtio_balloon
{
struct virtio_device *vdev;
@@ -360,6 +363,7 @@ static int virtballoon_probe(struct virtio_device *vdev)
init_waitqueue_head(&vb->config_change);
vb->vdev = vdev;
vb->need_stats_update = 0;
+ vdev->indirect_thresh = indirect_thresh;
err = init_vqs(vb);
if (err)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 5aa43c3..99a64a7 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -87,8 +87,11 @@ struct vring_virtqueue
/* Other side has made a mess, don't try any more. */
bool broken;
- /* Host supports indirect buffers */
- bool indirect;
+ /*
+ * Min. number of free space in the ring to trigger direct
+ * descriptor use
+ */
+ unsigned int indirect_thresh;
/* Host publishes avail event idx */
bool event;
@@ -216,9 +219,12 @@ int virtqueue_add_buf(struct virtqueue *_vq,
}
#endif
- /* If the host supports indirect descriptor tables, and we have multiple
- * buffers, then go indirect. FIXME: tune this threshold */
- if (vq->indirect && (out + in) > 1 && vq->num_free) {
+ /*
+ * If the host supports indirect descriptor tables, and we have multiple
+ * buffers, then go indirect.
+ */
+ if ((out + in) > 1 && vq->num_free &&
+ (vq->num_free < vq->indirect_thresh)) {
head = vring_add_indirect(vq, sg, out, in, gfp);
if (likely(head >= 0))
goto add_head;
@@ -647,13 +653,16 @@ struct virtqueue *vring_new_virtqueue(unsigned int num,
vq->broken = false;
vq->last_used_idx = 0;
vq->num_added = 0;
+ vq->indirect_thresh = 0;
list_add_tail(&vq->vq.list, &vdev->vqs);
#ifdef DEBUG
vq->in_use = false;
vq->last_add_time_valid = false;
#endif
- vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC);
+ if (virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC))
+ vq->indirect_thresh = vdev->indirect_thresh;
+
vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
/* No callback? Tell other side not to bother us. */
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 8efd28a..36019ec 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -69,6 +69,7 @@ struct virtio_device {
/* Note that this is a Linux set_bit-style bitmap. */
unsigned long features[1];
void *priv;
+ unsigned int indirect_thresh;
};
#define dev_to_virtio(dev) container_of(dev, struct virtio_device, dev)
diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
index 5af18d1..357bfba 100644
--- a/net/9p/trans_virtio.c
+++ b/net/9p/trans_virtio.c
@@ -52,6 +52,9 @@
#define VIRTQUEUE_NUM 128
+static unsigned int indirect_thresh = 0;
+module_param(indirect_thresh, uint, S_IRUGO);
+
/* a single mutex to manage channel initialization and attachment */
static DEFINE_MUTEX(virtio_9p_lock);
static DECLARE_WAIT_QUEUE_HEAD(vp_wq);
@@ -501,6 +504,7 @@ static int p9_virtio_probe(struct virtio_device *vdev)
chan->vdev = vdev;
/* We expect one virtqueue, for requests. */
+ vdev->indirect_thresh = indirect_thresh;
chan->vq = virtio_find_single_vq(vdev, req_done, "requests");
if (IS_ERR(chan->vq)) {
err = PTR_ERR(chan->vq);
--
1.7.8.6
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