#include <linux/errno.h>
#include <linux/init.h>
#include <linux/kernel.h>
+#include <linux/workqueue.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/netdevice.h>
#include <net/dst.h>
-/* Locking strategy:
- * 1) Garbage collection state of dead destination cache
- * entries is protected by dst_lock.
- * 2) GC is run only from BH context, and is the only remover
- * of entries.
- * 3) Entries are added to the garbage list from both BH
- * and non-BH context, so local BH disabling is needed.
- * 4) All operations modify state, so a spinlock is used.
+/*
+ * Theory of operations:
+ * 1) We use a list, protected by a spinlock, to add
+ * new entries from both BH and non-BH context.
+ * 2) In order to keep spinlock held for a small delay,
+ * we use a second list where are stored long lived
+ * entries, that are handled by the garbage collect thread
+ * fired by a workqueue.
+ * 3) This list is guarded by a mutex,
+ * so that the gc_task and dst_dev_event() can be synchronized.
*/
-static struct dst_entry *dst_garbage_list;
#if RT_CACHE_DEBUG >= 2
static atomic_t dst_total = ATOMIC_INIT(0);
#endif
-static DEFINE_SPINLOCK(dst_lock);
-static unsigned long dst_gc_timer_expires;
-static unsigned long dst_gc_timer_inc = DST_GC_MAX;
-static void dst_run_gc(unsigned long);
+/*
+ * We want to keep lock & list close together
+ * to dirty as few cache lines as possible in __dst_free().
+ * As this is not a very strong hint, we dont force an alignment on SMP.
+ */
+static struct {
+ spinlock_t lock;
+ struct dst_entry *list;
+ unsigned long timer_inc;
+ unsigned long timer_expires;
+} dst_garbage = {
+ .lock = __SPIN_LOCK_UNLOCKED(dst_garbage.lock),
+ .timer_inc = DST_GC_MAX,
+};
+static void dst_gc_task(struct work_struct *work);
static void ___dst_free(struct dst_entry * dst);
-static DEFINE_TIMER(dst_gc_timer, dst_run_gc, DST_GC_MIN, 0);
+static DECLARE_DELAYED_WORK(dst_gc_work, dst_gc_task);
-static void dst_run_gc(unsigned long dummy)
+static DEFINE_MUTEX(dst_gc_mutex);
+/*
+ * long lived entries are maintained in this list, guarded by dst_gc_mutex
+ */
+static struct dst_entry *dst_busy_list;
+
+static void dst_gc_task(struct work_struct *work)
{
int delayed = 0;
- int work_performed;
- struct dst_entry * dst, **dstp;
+ int work_performed = 0;
+ unsigned long expires = ~0L;
+ struct dst_entry *dst, *next, head;
+ struct dst_entry *last = &head;
+#if RT_CACHE_DEBUG >= 2
+ ktime_t time_start = ktime_get();
+ struct timespec elapsed;
+#endif
- if (!spin_trylock(&dst_lock)) {
- mod_timer(&dst_gc_timer, jiffies + HZ/10);
- return;
- }
+ mutex_lock(&dst_gc_mutex);
+ next = dst_busy_list;
- del_timer(&dst_gc_timer);
- dstp = &dst_garbage_list;
- work_performed = 0;
- while ((dst = *dstp) != NULL) {
- if (atomic_read(&dst->__refcnt)) {
- dstp = &dst->next;
+loop:
+ while ((dst = next) != NULL) {
+ next = dst->next;
+ prefetch(&next->next);
+ if (likely(atomic_read(&dst->__refcnt))) {
+ last->next = dst;
+ last = dst;
delayed++;
continue;
}
- *dstp = dst->next;
- work_performed = 1;
+ work_performed++;
dst = dst_destroy(dst);
if (dst) {
continue;
___dst_free(dst);
- dst->next = *dstp;
- *dstp = dst;
- dstp = &dst->next;
+ dst->next = next;
+ next = dst;
}
}
- if (!dst_garbage_list) {
- dst_gc_timer_inc = DST_GC_MAX;
- goto out;
+
+ spin_lock_bh(&dst_garbage.lock);
+ next = dst_garbage.list;
+ if (next) {
+ dst_garbage.list = NULL;
+ spin_unlock_bh(&dst_garbage.lock);
+ goto loop;
}
- if (!work_performed) {
- if ((dst_gc_timer_expires += dst_gc_timer_inc) > DST_GC_MAX)
- dst_gc_timer_expires = DST_GC_MAX;
- dst_gc_timer_inc += DST_GC_INC;
- } else {
- dst_gc_timer_inc = DST_GC_INC;
- dst_gc_timer_expires = DST_GC_MIN;
+ last->next = NULL;
+ dst_busy_list = head.next;
+ if (!dst_busy_list)
+ dst_garbage.timer_inc = DST_GC_MAX;
+ else {
+ /*
+ * if we freed less than 1/10 of delayed entries,
+ * we can sleep longer.
+ */
+ if (work_performed <= delayed/10) {
+ dst_garbage.timer_expires += dst_garbage.timer_inc;
+ if (dst_garbage.timer_expires > DST_GC_MAX)
+ dst_garbage.timer_expires = DST_GC_MAX;
+ dst_garbage.timer_inc += DST_GC_INC;
+ } else {
+ dst_garbage.timer_inc = DST_GC_INC;
+ dst_garbage.timer_expires = DST_GC_MIN;
+ }
+ expires = dst_garbage.timer_expires;
+ /*
+ * if the next desired timer is more than 4 seconds in the future
+ * then round the timer to whole seconds
+ */
+ if (expires > 4*HZ)
+ expires = round_jiffies_relative(expires);
+ schedule_delayed_work(&dst_gc_work, expires);
}
+
+ spin_unlock_bh(&dst_garbage.lock);
+ mutex_unlock(&dst_gc_mutex);
#if RT_CACHE_DEBUG >= 2
- printk("dst_total: %d/%d %ld\n",
- atomic_read(&dst_total), delayed, dst_gc_timer_expires);
+ elapsed = ktime_to_timespec(ktime_sub(ktime_get(), time_start));
+ printk(KERN_DEBUG "dst_total: %d delayed: %d work_perf: %d"
+ " expires: %lu elapsed: %lu us\n",
+ atomic_read(&dst_total), delayed, work_performed,
+ expires,
+ elapsed.tv_sec * USEC_PER_SEC + elapsed.tv_nsec / NSEC_PER_USEC);
#endif
- /* if the next desired timer is more than 4 seconds in the future
- * then round the timer to whole seconds
- */
- if (dst_gc_timer_expires > 4*HZ)
- mod_timer(&dst_gc_timer,
- round_jiffies(jiffies + dst_gc_timer_expires));
- else
- mod_timer(&dst_gc_timer, jiffies + dst_gc_timer_expires);
-
-out:
- spin_unlock(&dst_lock);
}
static int dst_discard(struct sk_buff *skb)
void __dst_free(struct dst_entry * dst)
{
- spin_lock_bh(&dst_lock);
+ spin_lock_bh(&dst_garbage.lock);
___dst_free(dst);
- dst->next = dst_garbage_list;
- dst_garbage_list = dst;
- if (dst_gc_timer_inc > DST_GC_INC) {
- dst_gc_timer_inc = DST_GC_INC;
- dst_gc_timer_expires = DST_GC_MIN;
- mod_timer(&dst_gc_timer, jiffies + dst_gc_timer_expires);
+ dst->next = dst_garbage.list;
+ dst_garbage.list = dst;
+ if (dst_garbage.timer_inc > DST_GC_INC) {
+ dst_garbage.timer_inc = DST_GC_INC;
+ dst_garbage.timer_expires = DST_GC_MIN;
+ schedule_delayed_work(&dst_gc_work, dst_garbage.timer_expires);
}
- spin_unlock_bh(&dst_lock);
+ spin_unlock_bh(&dst_garbage.lock);
}
struct dst_entry *dst_destroy(struct dst_entry * dst)
static int dst_dev_event(struct notifier_block *this, unsigned long event, void *ptr)
{
struct net_device *dev = ptr;
- struct dst_entry *dst;
+ struct dst_entry *dst, *last = NULL;
if (dev->nd_net != &init_net)
return NOTIFY_DONE;
switch (event) {
case NETDEV_UNREGISTER:
case NETDEV_DOWN:
- spin_lock_bh(&dst_lock);
- for (dst = dst_garbage_list; dst; dst = dst->next) {
+ mutex_lock(&dst_gc_mutex);
+ for (dst = dst_busy_list; dst; dst = dst->next) {
+ last = dst;
+ dst_ifdown(dst, dev, event != NETDEV_DOWN);
+ }
+
+ spin_lock_bh(&dst_garbage.lock);
+ dst = dst_garbage.list;
+ dst_garbage.list = NULL;
+ spin_unlock_bh(&dst_garbage.lock);
+
+ if (last)
+ last->next = dst;
+ else
+ dst_busy_list = dst;
+ for (; dst; dst = dst->next) {
dst_ifdown(dst, dev, event != NETDEV_DOWN);
}
- spin_unlock_bh(&dst_lock);
+ mutex_unlock(&dst_gc_mutex);
break;
}
return NOTIFY_DONE;
projects / linux-2.6 / commitdiff