xen/evtchn: improve scalability by using per-user locks
The global array of port users and the port_user_lock limits scalability of the evtchn device. Instead of the global array lookup, use a per-use (per-fd) tree of event channels bound by that user and protect the tree with a per-user lock. This is also a prerequiste for extended the number of supported event channels, by removing the fixed size, per-event channel array. Signed-off-by: David Vrabel <david.vrabel@citrix.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
David Vrabel
Konrad Rzeszutek Wilk
parent
65a45fa2f6
commit
73cc4bb0c7
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@ -57,6 +57,7 @@
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struct per_user_data {
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struct mutex bind_mutex; /* serialize bind/unbind operations */
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struct rb_root evtchns;
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/* Notification ring, accessed via /dev/xen/evtchn. */
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#define EVTCHN_RING_SIZE (PAGE_SIZE / sizeof(evtchn_port_t))
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@ -64,6 +65,7 @@ struct per_user_data {
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evtchn_port_t *ring;
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unsigned int ring_cons, ring_prod, ring_overflow;
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struct mutex ring_cons_mutex; /* protect against concurrent readers */
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spinlock_t ring_prod_lock; /* product against concurrent interrupts */
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/* Processes wait on this queue when ring is empty. */
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wait_queue_head_t evtchn_wait;
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@ -71,54 +73,79 @@ struct per_user_data {
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const char *name;
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};
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/*
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* Who's bound to each port? This is logically an array of struct
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* per_user_data *, but we encode the current enabled-state in bit 0.
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*/
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static unsigned long *port_user;
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static DEFINE_SPINLOCK(port_user_lock); /* protects port_user[] and ring_prod */
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struct user_evtchn {
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struct rb_node node;
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struct per_user_data *user;
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unsigned port;
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bool enabled;
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};
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static inline struct per_user_data *get_port_user(unsigned port)
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static int add_evtchn(struct per_user_data *u, struct user_evtchn *evtchn)
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{
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return (struct per_user_data *)(port_user[port] & ~1);
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struct rb_node **new = &(u->evtchns.rb_node), *parent = NULL;
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while (*new) {
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struct user_evtchn *this;
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this = container_of(*new, struct user_evtchn, node);
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parent = *new;
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if (this->port < evtchn->port)
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new = &((*new)->rb_left);
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else if (this->port > evtchn->port)
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new = &((*new)->rb_right);
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else
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return -EEXIST;
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}
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/* Add new node and rebalance tree. */
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rb_link_node(&evtchn->node, parent, new);
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rb_insert_color(&evtchn->node, &u->evtchns);
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return 0;
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}
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static inline void set_port_user(unsigned port, struct per_user_data *u)
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static void del_evtchn(struct per_user_data *u, struct user_evtchn *evtchn)
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{
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port_user[port] = (unsigned long)u;
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rb_erase(&evtchn->node, &u->evtchns);
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kfree(evtchn);
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}
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static inline bool get_port_enabled(unsigned port)
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static struct user_evtchn *find_evtchn(struct per_user_data *u, unsigned port)
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{
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return port_user[port] & 1;
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}
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struct rb_node *node = u->evtchns.rb_node;
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static inline void set_port_enabled(unsigned port, bool enabled)
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{
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if (enabled)
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port_user[port] |= 1;
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else
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port_user[port] &= ~1;
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while (node) {
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struct user_evtchn *evtchn;
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evtchn = container_of(node, struct user_evtchn, node);
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if (evtchn->port < port)
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node = node->rb_left;
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else if (evtchn->port > port)
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node = node->rb_right;
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else
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return evtchn;
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}
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return NULL;
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}
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static irqreturn_t evtchn_interrupt(int irq, void *data)
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{
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unsigned int port = (unsigned long)data;
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struct per_user_data *u;
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struct user_evtchn *evtchn = data;
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struct per_user_data *u = evtchn->user;
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spin_lock(&port_user_lock);
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u = get_port_user(port);
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WARN(!get_port_enabled(port),
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WARN(!evtchn->enabled,
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"Interrupt for port %d, but apparently not enabled; per-user %p\n",
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port, u);
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evtchn->port, u);
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disable_irq_nosync(irq);
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set_port_enabled(port, false);
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evtchn->enabled = false;
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spin_lock(&u->ring_prod_lock);
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if ((u->ring_prod - u->ring_cons) < EVTCHN_RING_SIZE) {
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u->ring[EVTCHN_RING_MASK(u->ring_prod)] = port;
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u->ring[EVTCHN_RING_MASK(u->ring_prod)] = evtchn->port;
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wmb(); /* Ensure ring contents visible */
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if (u->ring_cons == u->ring_prod++) {
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wake_up_interruptible(&u->evtchn_wait);
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@ -128,7 +155,7 @@ static irqreturn_t evtchn_interrupt(int irq, void *data)
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} else
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u->ring_overflow = 1;
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spin_unlock(&port_user_lock);
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spin_unlock(&u->ring_prod_lock);
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return IRQ_HANDLED;
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}
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@ -229,20 +256,20 @@ static ssize_t evtchn_write(struct file *file, const char __user *buf,
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if (copy_from_user(kbuf, buf, count) != 0)
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goto out;
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spin_lock_irq(&port_user_lock);
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mutex_lock(&u->bind_mutex);
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for (i = 0; i < (count/sizeof(evtchn_port_t)); i++) {
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unsigned port = kbuf[i];
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struct user_evtchn *evtchn;
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if (port < NR_EVENT_CHANNELS &&
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get_port_user(port) == u &&
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!get_port_enabled(port)) {
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set_port_enabled(port, true);
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evtchn = find_evtchn(u, port);
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if (evtchn && !evtchn->enabled) {
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evtchn->enabled = true;
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enable_irq(irq_from_evtchn(port));
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}
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}
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spin_unlock_irq(&port_user_lock);
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mutex_unlock(&u->bind_mutex);
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rc = count;
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@ -253,6 +280,8 @@ static ssize_t evtchn_write(struct file *file, const char __user *buf,
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static int evtchn_bind_to_user(struct per_user_data *u, int port)
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{
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struct user_evtchn *evtchn;
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struct evtchn_close close;
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int rc = 0;
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/*
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@ -263,35 +292,47 @@ static int evtchn_bind_to_user(struct per_user_data *u, int port)
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* interrupt handler yet, and our caller has already
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* serialized bind operations.)
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*/
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BUG_ON(get_port_user(port) != NULL);
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set_port_user(port, u);
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set_port_enabled(port, true); /* start enabled */
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evtchn = kzalloc(sizeof(*evtchn), GFP_KERNEL);
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if (!evtchn)
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return -ENOMEM;
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evtchn->user = u;
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evtchn->port = port;
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evtchn->enabled = true; /* start enabled */
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rc = add_evtchn(u, evtchn);
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if (rc < 0)
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goto err;
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rc = bind_evtchn_to_irqhandler(port, evtchn_interrupt, IRQF_DISABLED,
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u->name, (void *)(unsigned long)port);
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if (rc >= 0)
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rc = evtchn_make_refcounted(port);
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else {
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/* bind failed, should close the port now */
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struct evtchn_close close;
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close.port = port;
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if (HYPERVISOR_event_channel_op(EVTCHNOP_close, &close) != 0)
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BUG();
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set_port_user(port, NULL);
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}
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u->name, evtchn);
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if (rc < 0)
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goto err;
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rc = evtchn_make_refcounted(port);
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return rc;
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err:
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/* bind failed, should close the port now */
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close.port = port;
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if (HYPERVISOR_event_channel_op(EVTCHNOP_close, &close) != 0)
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BUG();
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del_evtchn(u, evtchn);
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kfree(evtchn);
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return rc;
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}
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static void evtchn_unbind_from_user(struct per_user_data *u, int port)
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static void evtchn_unbind_from_user(struct per_user_data *u,
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struct user_evtchn *evtchn)
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{
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int irq = irq_from_evtchn(port);
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int irq = irq_from_evtchn(evtchn->port);
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BUG_ON(irq < 0);
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unbind_from_irqhandler(irq, (void *)(unsigned long)port);
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unbind_from_irqhandler(irq, evtchn);
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set_port_user(port, NULL);
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del_evtchn(u, evtchn);
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}
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static long evtchn_ioctl(struct file *file,
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@ -370,6 +411,7 @@ static long evtchn_ioctl(struct file *file,
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case IOCTL_EVTCHN_UNBIND: {
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struct ioctl_evtchn_unbind unbind;
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struct user_evtchn *evtchn;
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rc = -EFAULT;
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if (copy_from_user(&unbind, uarg, sizeof(unbind)))
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@ -380,29 +422,27 @@ static long evtchn_ioctl(struct file *file,
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break;
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rc = -ENOTCONN;
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if (get_port_user(unbind.port) != u)
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evtchn = find_evtchn(u, unbind.port);
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if (!evtchn)
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break;
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disable_irq(irq_from_evtchn(unbind.port));
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evtchn_unbind_from_user(u, unbind.port);
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evtchn_unbind_from_user(u, evtchn);
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rc = 0;
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break;
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}
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case IOCTL_EVTCHN_NOTIFY: {
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struct ioctl_evtchn_notify notify;
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struct user_evtchn *evtchn;
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rc = -EFAULT;
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if (copy_from_user(¬ify, uarg, sizeof(notify)))
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break;
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if (notify.port >= NR_EVENT_CHANNELS) {
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rc = -EINVAL;
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} else if (get_port_user(notify.port) != u) {
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rc = -ENOTCONN;
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} else {
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rc = -ENOTCONN;
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evtchn = find_evtchn(u, notify.port);
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if (evtchn) {
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notify_remote_via_evtchn(notify.port);
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rc = 0;
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}
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@ -412,9 +452,9 @@ static long evtchn_ioctl(struct file *file,
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case IOCTL_EVTCHN_RESET: {
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/* Initialise the ring to empty. Clear errors. */
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mutex_lock(&u->ring_cons_mutex);
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spin_lock_irq(&port_user_lock);
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spin_lock_irq(&u->ring_prod_lock);
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u->ring_cons = u->ring_prod = u->ring_overflow = 0;
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spin_unlock_irq(&port_user_lock);
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spin_unlock_irq(&u->ring_prod_lock);
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mutex_unlock(&u->ring_cons_mutex);
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rc = 0;
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break;
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@ -473,6 +513,7 @@ static int evtchn_open(struct inode *inode, struct file *filp)
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mutex_init(&u->bind_mutex);
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mutex_init(&u->ring_cons_mutex);
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spin_lock_init(&u->ring_prod_lock);
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filp->private_data = u;
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@ -481,15 +522,15 @@ static int evtchn_open(struct inode *inode, struct file *filp)
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static int evtchn_release(struct inode *inode, struct file *filp)
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{
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int i;
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struct per_user_data *u = filp->private_data;
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struct rb_node *node;
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for (i = 0; i < NR_EVENT_CHANNELS; i++) {
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if (get_port_user(i) != u)
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continue;
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while ((node = u->evtchns.rb_node)) {
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struct user_evtchn *evtchn;
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disable_irq(irq_from_evtchn(i));
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evtchn_unbind_from_user(get_port_user(i), i);
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evtchn = rb_entry(node, struct user_evtchn, node);
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disable_irq(irq_from_evtchn(evtchn->port));
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evtchn_unbind_from_user(u, evtchn);
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}
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free_page((unsigned long)u->ring);
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@ -523,12 +564,6 @@ static int __init evtchn_init(void)
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if (!xen_domain())
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return -ENODEV;
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port_user = kcalloc(NR_EVENT_CHANNELS, sizeof(*port_user), GFP_KERNEL);
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if (port_user == NULL)
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return -ENOMEM;
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spin_lock_init(&port_user_lock);
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/* Create '/dev/xen/evtchn'. */
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err = misc_register(&evtchn_miscdev);
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if (err != 0) {
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@ -543,9 +578,6 @@ static int __init evtchn_init(void)
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static void __exit evtchn_cleanup(void)
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{
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kfree(port_user);
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port_user = NULL;
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misc_deregister(&evtchn_miscdev);
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}
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