[PATCH 4.9 051/103] vhost: introduce vhost_exceeds_weight()

Greg Kroah-Hartman
2019-08-22T17:43:51Z

From: Jason Wang <jasowang@redhat.com>

commit e82b9b0727ff6d665fff2d326162b460dded554d upstream.

We used to have vhost_exceeds_weight() for vhost-net to:

- prevent vhost kthread from hogging the cpu
- balance the time spent between TX and RX

This function could be useful for vsock and scsi as well. So move it
to vhost.c. Device must specify a weight which counts the number of
requests, or it can also specific a byte_weight which counts the
number of bytes that has been processed.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
[bwh: Backported to 4.9:
- In vhost_net, both Tx modes are handled in one loop in handle_tx()
- Adjust context]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/vhost/net.c | 18 +++++-------------
drivers/vhost/scsi.c | 9 ++++++++-
drivers/vhost/vhost.c | 20 +++++++++++++++++++-
drivers/vhost/vhost.h | 6 +++++-
drivers/vhost/vsock.c | 12 +++++++++++-
5 files changed, 48 insertions(+), 17 deletions(-)

--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -357,12 +357,6 @@ static int vhost_net_tx_get_vq_desc(stru
return r;
}

-static bool vhost_exceeds_weight(int pkts, int total_len)
-{
- return total_len >= VHOST_NET_WEIGHT ||
- pkts >= VHOST_NET_PKT_WEIGHT;
-}
-
/* Expects to be always run from workqueue - which acts as
* read-size critical section for our kind of RCU. */
static void handle_tx(struct vhost_net *net)
@@ -487,10 +481,9 @@ static void handle_tx(struct vhost_net *
vhost_zerocopy_signal_used(net, vq);
total_len += len;
vhost_net_tx_packet(net);
- if (unlikely(vhost_exceeds_weight(++sent_pkts, total_len))) {
- vhost_poll_queue(&vq->poll);
+ if (unlikely(vhost_exceeds_weight(vq, ++sent_pkts,
+ total_len)))
break;
- }
}
out:
mutex_unlock(&vq->mutex);
@@ -768,10 +761,8 @@ static void handle_rx(struct vhost_net *
vhost_log_write(vq, vq_log, log, vhost_len,
vq->iov, in);
total_len += vhost_len;
- if (unlikely(vhost_exceeds_weight(++recv_pkts, total_len))) {
- vhost_poll_queue(&vq->poll);
+ if (unlikely(vhost_exceeds_weight(vq, ++recv_pkts, total_len)))
goto out;
- }
}
vhost_net_enable_vq(net, vq);
out:
@@ -842,7 +833,8 @@ static int vhost_net_open(struct inode *
n->vqs[i].vhost_hlen = 0;
n->vqs[i].sock_hlen = 0;
}
- vhost_dev_init(dev, vqs, VHOST_NET_VQ_MAX);
+ vhost_dev_init(dev, vqs, VHOST_NET_VQ_MAX,
+ VHOST_NET_WEIGHT, VHOST_NET_PKT_WEIGHT);

vhost_poll_init(n->poll + VHOST_NET_VQ_TX, handle_tx_net, POLLOUT, dev);
vhost_poll_init(n->poll + VHOST_NET_VQ_RX, handle_rx_net, POLLIN, dev);
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -58,6 +58,12 @@
#define VHOST_SCSI_PREALLOC_UPAGES 2048
#define VHOST_SCSI_PREALLOC_PROT_SGLS 512

+/* Max number of requests before requeueing the job.
+ * Using this limit prevents one virtqueue from starving others with
+ * request.
+ */
+#define VHOST_SCSI_WEIGHT 256
+
struct vhost_scsi_inflight {
/* Wait for the flush operation to finish */
struct completion comp;
@@ -1433,7 +1439,8 @@ static int vhost_scsi_open(struct inode
vqs[i] = &vs->vqs[i].vq;
vs->vqs[i].vq.handle_kick = vhost_scsi_handle_kick;
}
- vhost_dev_init(&vs->dev, vqs, VHOST_SCSI_MAX_VQ);
+ vhost_dev_init(&vs->dev, vqs, VHOST_SCSI_MAX_VQ,
+ VHOST_SCSI_WEIGHT, 0);

vhost_scsi_init_inflight(vs, NULL);

--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -393,8 +393,24 @@ static void vhost_dev_free_iovecs(struct
vhost_vq_free_iovecs(dev->vqs[i]);
}

+bool vhost_exceeds_weight(struct vhost_virtqueue *vq,
+ int pkts, int total_len)
+{
+ struct vhost_dev *dev = vq->dev;
+
+ if ((dev->byte_weight && total_len >= dev->byte_weight) ||
+ pkts >= dev->weight) {
+ vhost_poll_queue(&vq->poll);
+ return true;
+ }
+
+ return false;
+}
+EXPORT_SYMBOL_GPL(vhost_exceeds_weight);
+
void vhost_dev_init(struct vhost_dev *dev,
- struct vhost_virtqueue **vqs, int nvqs)
+ struct vhost_virtqueue **vqs, int nvqs,
+ int weight, int byte_weight)
{
struct vhost_virtqueue *vq;
int i;
@@ -408,6 +424,8 @@ void vhost_dev_init(struct vhost_dev *de
dev->iotlb = NULL;
dev->mm = NULL;
dev->worker = NULL;
+ dev->weight = weight;
+ dev->byte_weight = byte_weight;
init_llist_head(&dev->work_list);
init_waitqueue_head(&dev->wait);
INIT_LIST_HEAD(&dev->read_list);
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -164,9 +164,13 @@ struct vhost_dev {
struct list_head read_list;
struct list_head pending_list;
wait_queue_head_t wait;
+ int weight;
+ int byte_weight;
};

-void vhost_dev_init(struct vhost_dev *, struct vhost_virtqueue **vqs, int nvqs);
+bool vhost_exceeds_weight(struct vhost_virtqueue *vq, int pkts, int total_len);
+void vhost_dev_init(struct vhost_dev *, struct vhost_virtqueue **vqs,
+ int nvqs, int weight, int byte_weight);
long vhost_dev_set_owner(struct vhost_dev *dev);
bool vhost_dev_has_owner(struct vhost_dev *dev);
long vhost_dev_check_owner(struct vhost_dev *);
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -21,6 +21,14 @@
#include "vhost.h"

#define VHOST_VSOCK_DEFAULT_HOST_CID 2
+/* Max number of bytes transferred before requeueing the job.
+ * Using this limit prevents one virtqueue from starving others. */
+#define VHOST_VSOCK_WEIGHT 0x80000
+/* Max number of packets transferred before requeueing the job.
+ * Using this limit prevents one virtqueue from starving others with
+ * small pkts.
+ */
+#define VHOST_VSOCK_PKT_WEIGHT 256

enum {
VHOST_VSOCK_FEATURES = VHOST_FEATURES,
@@ -529,7 +537,9 @@ static int vhost_vsock_dev_open(struct i
vsock->vqs[VSOCK_VQ_TX].handle_kick = vhost_vsock_handle_tx_kick;
vsock->vqs[VSOCK_VQ_RX].handle_kick = vhost_vsock_handle_rx_kick;

- vhost_dev_init(&vsock->dev, vqs, ARRAY_SIZE(vsock->vqs));
+ vhost_dev_init(&vsock->dev, vqs, ARRAY_SIZE(vsock->vqs),
+ VHOST_VSOCK_PKT_WEIGHT,
+ VHOST_VSOCK_WEIGHT);

file->private_data = vsock;
spin_lock_init(&vsock->send_pkt_list_lock);