1 files changed, 41 insertions, 8 deletions

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index df2f5a3901df..0f87e5d21be7 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -76,6 +76,7 @@ struct conntrack_gc_work {
 	struct delayed_work	dwork;
 	u32			last_bucket;
 	bool			exiting;
+	long			next_gc_run;
 };
 
 static __read_mostly struct kmem_cache *nf_conntrack_cachep;
@@ -83,9 +84,11 @@ static __read_mostly spinlock_t nf_conntrack_locks_all_lock;
 static __read_mostly DEFINE_SPINLOCK(nf_conntrack_locks_all_lock);
 static __read_mostly bool nf_conntrack_locks_all;
 
+/* every gc cycle scans at most 1/GC_MAX_BUCKETS_DIV part of table */
 #define GC_MAX_BUCKETS_DIV	64u
-#define GC_MAX_BUCKETS		8192u
-#define GC_INTERVAL		(5 * HZ)
+/* upper bound of scan intervals */
+#define GC_INTERVAL_MAX		(2 * HZ)
+/* maximum conntracks to evict per gc run */
 #define GC_MAX_EVICTS		256u
 
 static struct conntrack_gc_work conntrack_gc_work;
@@ -936,13 +939,13 @@ static noinline int early_drop(struct net *net, unsigned int _hash)
 static void gc_worker(struct work_struct *work)
 {
 	unsigned int i, goal, buckets = 0, expired_count = 0;
-	unsigned long next_run = GC_INTERVAL;
-	unsigned int ratio, scanned = 0;
 	struct conntrack_gc_work *gc_work;
+	unsigned int ratio, scanned = 0;
+	unsigned long next_run;
 
 	gc_work = container_of(work, struct conntrack_gc_work, dwork.work);
 
-	goal = min(nf_conntrack_htable_size / GC_MAX_BUCKETS_DIV, GC_MAX_BUCKETS);
+	goal = nf_conntrack_htable_size / GC_MAX_BUCKETS_DIV;
 	i = gc_work->last_bucket;
 
 	do {
@@ -982,17 +985,47 @@ static void gc_worker(struct work_struct *work)
 	if (gc_work->exiting)
 		return;
 
+	/*
+	 * Eviction will normally happen from the packet path, and not
+	 * from this gc worker.
+	 *
+	 * This worker is only here to reap expired entries when system went
+	 * idle after a busy period.
+	 *
+	 * The heuristics below are supposed to balance conflicting goals:
+	 *
+	 * 1. Minimize time until we notice a stale entry
+	 * 2. Maximize scan intervals to not waste cycles
+	 *
+	 * Normally, expired_count will be 0, this increases the next_run time
+	 * to priorize 2) above.
+	 *
+	 * As soon as a timed-out entry is found, move towards 1) and increase
+	 * the scan frequency.
+	 * In case we have lots of evictions next scan is done immediately.
+	 */
 	ratio = scanned ? expired_count * 100 / scanned : 0;
-	if (ratio >= 90 || expired_count == GC_MAX_EVICTS)
+	if (ratio >= 90 || expired_count == GC_MAX_EVICTS) {
+		gc_work->next_gc_run = 0;
 		next_run = 0;
+	} else if (expired_count) {
+		gc_work->next_gc_run /= 2U;
+		next_run = msecs_to_jiffies(1);
+	} else {
+		if (gc_work->next_gc_run < GC_INTERVAL_MAX)
+			gc_work->next_gc_run += msecs_to_jiffies(1);
+
+		next_run = gc_work->next_gc_run;
+	}
 
 	gc_work->last_bucket = i;
-	schedule_delayed_work(&gc_work->dwork, next_run);
+	queue_delayed_work(system_long_wq, &gc_work->dwork, next_run);
 }
 
 static void conntrack_gc_work_init(struct conntrack_gc_work *gc_work)
 {
 	INIT_DELAYED_WORK(&gc_work->dwork, gc_worker);
+	gc_work->next_gc_run = GC_INTERVAL_MAX;
 	gc_work->exiting = false;
 }
 
@@ -1885,7 +1918,7 @@ int nf_conntrack_init_start(void)
 	nf_ct_untracked_status_or(IPS_CONFIRMED | IPS_UNTRACKED);
 
 	conntrack_gc_work_init(&conntrack_gc_work);
-	schedule_delayed_work(&conntrack_gc_work.dwork, GC_INTERVAL);
+	queue_delayed_work(system_long_wq, &conntrack_gc_work.dwork, GC_INTERVAL_MAX);
 
 	return 0;