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Subject[RFC PATCH] xen-netback: making the bandwidth limiter runtime settable
Date
From: "Palik, Imre" <imrep@amazon.de>

With the current netback, the bandwidth limiter's parameters are only
settable during vif setup time. This patch register a watch on them, and
thus makes them runtime changeable.

When the watch fires, the timer is reset. The timer's mutex is used for
fencing the change.

Cc: Anthony Liguori <aliguori@amazon.com>
Signed-off-by: Imre Palik <imrep@amazon.de>
---
drivers/net/xen-netback/common.h | 4 ++
drivers/net/xen-netback/interface.c | 1 +
drivers/net/xen-netback/netback.c | 4 +-
drivers/net/xen-netback/xenbus.c | 73 +++++++++++++++++++++++++++++++----
4 files changed, 73 insertions(+), 9 deletions(-)

diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index 589fa25..8a495b3 100644
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -238,6 +238,8 @@ struct xenvif {
unsigned int num_queues; /* active queues, resource allocated */
unsigned int stalled_queues;

+ struct xenbus_watch credit_watch;
+
spinlock_t lock;

#ifdef CONFIG_DEBUG_FS
@@ -260,6 +262,8 @@ static inline struct xenbus_device *xenvif_to_xenbus_device(struct xenvif *vif)
return to_xenbus_device(vif->dev->dev.parent);
}

+void xenvif_tx_credit_callback(unsigned long data);
+
struct xenvif *xenvif_alloc(struct device *parent,
domid_t domid,
unsigned int handle);
diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index 3aa8648..34d8038 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -463,6 +463,7 @@ int xenvif_init_queue(struct xenvif_queue *queue)
queue->credit_bytes = queue->remaining_credit = ~0UL;
queue->credit_usec = 0UL;
init_timer(&queue->credit_timeout);
+ queue->credit_timeout.function = xenvif_tx_credit_callback;
queue->credit_window_start = get_jiffies_64();

queue->rx_queue_max = XENVIF_RX_QUEUE_BYTES;
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index cab9f52..bcc1880 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -641,7 +641,7 @@ static void tx_add_credit(struct xenvif_queue *queue)
queue->remaining_credit = min(max_credit, max_burst);
}

-static void tx_credit_callback(unsigned long data)
+void xenvif_tx_credit_callback(unsigned long data)
{
struct xenvif_queue *queue = (struct xenvif_queue *)data;
tx_add_credit(queue);
@@ -1170,7 +1170,7 @@ static bool tx_credit_exceeded(struct xenvif_queue *queue, unsigned size)
queue->credit_timeout.data =
(unsigned long)queue;
queue->credit_timeout.function =
- tx_credit_callback;
+ xenvif_tx_credit_callback;
mod_timer(&queue->credit_timeout,
next_credit);
queue->credit_window_start = next_credit;
diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
index 794204e..c6528de 100644
--- a/drivers/net/xen-netback/xenbus.c
+++ b/drivers/net/xen-netback/xenbus.c
@@ -41,6 +41,7 @@ static void connect(struct backend_info *be);
static int read_xenbus_vif_flags(struct backend_info *be);
static int backend_create_xenvif(struct backend_info *be);
static void unregister_hotplug_status_watch(struct backend_info *be);
+static void xen_unregister_watchers(struct xenvif *vif);
static void set_backend_state(struct backend_info *be,
enum xenbus_state state);

@@ -232,6 +233,7 @@ static int netback_remove(struct xenbus_device *dev)
unregister_hotplug_status_watch(be);
if (be->vif) {
kobject_uevent(&dev->dev.kobj, KOBJ_OFFLINE);
+ xen_unregister_watchers(be->vif);
xenbus_rm(XBT_NIL, dev->nodename, "hotplug-status");
xenvif_free(be->vif);
be->vif = NULL;
@@ -430,6 +432,7 @@ static int backend_create_xenvif(struct backend_info *be)
static void backend_disconnect(struct backend_info *be)
{
if (be->vif) {
+ xen_unregister_watchers(be->vif);
#ifdef CONFIG_DEBUG_FS
xenvif_debugfs_delif(be->vif);
#endif /* CONFIG_DEBUG_FS */
@@ -594,13 +597,9 @@ static void xen_net_read_rate(struct xenbus_device *dev,
unsigned long b, u;
char *ratestr;

- /* Default to unlimited bandwidth. */
- *bytes = ~0UL;
- *usec = 0;
-
ratestr = xenbus_read(XBT_NIL, dev->nodename, "rate", NULL);
if (IS_ERR(ratestr))
- return;
+ goto reset;

s = ratestr;
b = simple_strtoul(s, &e, 10);
@@ -612,15 +611,21 @@ static void xen_net_read_rate(struct xenbus_device *dev,
if ((s == e) || (*e != '\0'))
goto fail;

+ kfree(ratestr);
+
*bytes = b;
*usec = u;

- kfree(ratestr);
return;

- fail:
+fail:
pr_warn("Failed to parse network rate limit. Traffic unlimited.\n");
kfree(ratestr);
+
+reset:
+ /* Default to unlimited bandwidth. */
+ *bytes = ~0UL;
+ *usec = 0;
}

static int xen_net_read_mac(struct xenbus_device *dev, u8 mac[])
@@ -645,6 +650,59 @@ static int xen_net_read_mac(struct xenbus_device *dev, u8 mac[])
return 0;
}

+static void xen_net_rate_changed(struct xenbus_watch *watch,
+ const char **vec, unsigned int len)
+{
+ struct xenvif *vif = container_of(watch, struct xenvif, credit_watch);
+ struct xenbus_device *dev = xenvif_to_xenbus_device(vif);
+ unsigned long credit_bytes;
+ unsigned long credit_usec;
+ unsigned int queue_index;
+
+ xen_net_read_rate(dev, &credit_bytes, &credit_usec);
+ for (queue_index = 0; queue_index < vif->num_queues; queue_index++) {
+ struct xenvif_queue *queue = &vif->queues[queue_index];
+
+ queue->credit_bytes = credit_bytes;
+ queue->credit_usec = credit_usec;
+ if (!mod_timer_pending(&queue->credit_timeout, jiffies) &&
+ queue->remaining_credit > queue->credit_bytes) {
+ queue->remaining_credit = queue->credit_bytes;
+ }
+ }
+}
+
+static int xen_register_watchers(struct xenbus_device *dev, struct xenvif *vif)
+{
+ int err = 0;
+ char *node;
+ unsigned maxlen = strlen(dev->nodename) + sizeof("/rate");
+
+ node = kmalloc(maxlen, GFP_KERNEL);
+ if (!node)
+ return -ENOMEM;
+ sprintf(node, "%s/rate", dev->nodename);
+ vif->credit_watch.node = node;
+ vif->credit_watch.callback = xen_net_rate_changed;
+ err = register_xenbus_watch(&vif->credit_watch);
+ if (err) {
+ pr_err("Failed to set watcher %s\n", vif->credit_watch.node);
+ kfree(node);
+ vif->credit_watch.node = 0;
+ vif->credit_watch.callback = 0;
+ }
+ return err;
+}
+
+static void xen_unregister_watchers(struct xenvif *vif)
+{
+ if (vif->credit_watch.node) {
+ unregister_xenbus_watch(&vif->credit_watch);
+ kfree(vif->credit_watch.node);
+ vif->credit_watch.node = NULL;
+ }
+}
+
static void unregister_hotplug_status_watch(struct backend_info *be)
{
if (be->have_hotplug_status_watch) {
@@ -709,6 +767,7 @@ static void connect(struct backend_info *be)
}

xen_net_read_rate(dev, &credit_bytes, &credit_usec);
+ xen_register_watchers(dev, be->vif);
read_xenbus_vif_flags(be);

/* Use the number of queues requested by the frontend */
--
1.7.9.5


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