tcp/dccp: get rid of central timewait timer

Using a timer wheel for timewait sockets was nice ~15 years ago when
memory was expensive and machines had a single processor.

This does not scale, code is ugly and source of huge latencies
(Typically 30 ms have been seen, cpus spinning on death_lock spinlock.)

We can afford to use an extra 64 bytes per timewait sock and spread
timewait load to all cpus to have better behavior.

Tested:

On following test, /proc/sys/net/ipv4/tcp_tw_recycle is set to 1
on the target (lpaa24)

Before patch :

lpaa23:~# ./super_netperf 200 -H lpaa24 -t TCP_CC -l 60 -- -p0,0
419594

lpaa23:~# ./super_netperf 200 -H lpaa24 -t TCP_CC -l 60 -- -p0,0
437171

While test is running, we can observe 25 or even 33 ms latencies.

lpaa24:~# ping -c 1000 -i 0.02 -qn lpaa23
...
1000 packets transmitted, 1000 received, 0% packet loss, time 20601ms
rtt min/avg/max/mdev = 0.020/0.217/25.771/1.535 ms, pipe 2

lpaa24:~# ping -c 1000 -i 0.02 -qn lpaa23
...
1000 packets transmitted, 1000 received, 0% packet loss, time 20702ms
rtt min/avg/max/mdev = 0.019/0.183/33.761/1.441 ms, pipe 2

After patch :

About 90% increase of throughput :

lpaa23:~# ./super_netperf 200 -H lpaa24 -t TCP_CC -l 60 -- -p0,0
810442

lpaa23:~# ./super_netperf 200 -H lpaa24 -t TCP_CC -l 60 -- -p0,0
800992

And latencies are kept to minimal values during this load, even
if network utilization is 90% higher :

lpaa24:~# ping -c 1000 -i 0.02 -qn lpaa23
...
1000 packets transmitted, 1000 received, 0% packet loss, time 19991ms
rtt min/avg/max/mdev = 0.023/0.064/0.360/0.042 ms

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 9 insertions, 98 deletions

diff --git a/include/net/inet_timewait_sock.h b/include/net/inet_timewait_sock.h
index b7ce100..360c480 100644
--- a/include/net/inet_timewait_sock.h
+++ b/include/net/inet_timewait_sock.h
@@ -31,67 +31,14 @@
 
 struct inet_hashinfo;
 
-#define INET_TWDR_RECYCLE_SLOTS_LOG	5
-#define INET_TWDR_RECYCLE_SLOTS		(1 << INET_TWDR_RECYCLE_SLOTS_LOG)
-
-/*
- * If time > 4sec, it is "slow" path, no recycling is required,
- * so that we select tick to get range about 4 seconds.
- */
-#if HZ <= 16 || HZ > 4096
-# error Unsupported: HZ <= 16 or HZ > 4096
-#elif HZ <= 32
-# define INET_TWDR_RECYCLE_TICK (5 + 2 - INET_TWDR_RECYCLE_SLOTS_LOG)
-#elif HZ <= 64
-# define INET_TWDR_RECYCLE_TICK (6 + 2 - INET_TWDR_RECYCLE_SLOTS_LOG)
-#elif HZ <= 128
-# define INET_TWDR_RECYCLE_TICK (7 + 2 - INET_TWDR_RECYCLE_SLOTS_LOG)
-#elif HZ <= 256
-# define INET_TWDR_RECYCLE_TICK (8 + 2 - INET_TWDR_RECYCLE_SLOTS_LOG)
-#elif HZ <= 512
-# define INET_TWDR_RECYCLE_TICK (9 + 2 - INET_TWDR_RECYCLE_SLOTS_LOG)
-#elif HZ <= 1024
-# define INET_TWDR_RECYCLE_TICK (10 + 2 - INET_TWDR_RECYCLE_SLOTS_LOG)
-#elif HZ <= 2048
-# define INET_TWDR_RECYCLE_TICK (11 + 2 - INET_TWDR_RECYCLE_SLOTS_LOG)
-#else
-# define INET_TWDR_RECYCLE_TICK (12 + 2 - INET_TWDR_RECYCLE_SLOTS_LOG)
-#endif
-
-static inline u32 inet_tw_time_stamp(void)
-{
-	return jiffies;
-}
-
-/* TIME_WAIT reaping mechanism. */
-#define INET_TWDR_TWKILL_SLOTS	8 /* Please keep this a power of 2. */
-
-#define INET_TWDR_TWKILL_QUOTA 100
-
 struct inet_timewait_death_row {
-	/* Short-time timewait calendar */
-	int			twcal_hand;
-	unsigned long		twcal_jiffie;
-	struct timer_list	twcal_timer;
-	struct hlist_head	twcal_row[INET_TWDR_RECYCLE_SLOTS];
-
-	spinlock_t		death_lock;
-	int			tw_count;
-	int			period;
-	u32			thread_slots;
-	struct work_struct	twkill_work;
-	struct timer_list	tw_timer;
-	int			slot;
-	struct hlist_head	cells[INET_TWDR_TWKILL_SLOTS];
-	struct inet_hashinfo 	*hashinfo;
+	atomic_t		tw_count;
+
+	struct inet_hashinfo 	*hashinfo ____cacheline_aligned_in_smp;
 	int			sysctl_tw_recycle;
 	int			sysctl_max_tw_buckets;
 };
 
-void inet_twdr_hangman(unsigned long data);
-void inet_twdr_twkill_work(struct work_struct *work);
-void inet_twdr_twcal_tick(unsigned long data);
-
 struct inet_bind_bucket;
 
 /*
@@ -133,52 +80,18 @@ struct inet_timewait_sock {
 	__be16			tw_sport;
 	kmemcheck_bitfield_begin(flags);
 	/* And these are ours. */
-	unsigned int		tw_pad0		: 1,	/* 1 bit hole */
+	unsigned int		tw_kill		: 1,
 				tw_transparent  : 1,
 				tw_flowlabel	: 20,
 				tw_pad		: 2,	/* 2 bits hole */
 				tw_tos		: 8;
 	kmemcheck_bitfield_end(flags);
-	u32			tw_ttd;
+	struct timer_list	tw_timer;
 	struct inet_bind_bucket	*tw_tb;
-	struct hlist_node	tw_death_node;
+	struct inet_timewait_death_row *tw_dr;
 };
 #define tw_tclass tw_tos
 
-static inline int inet_twsk_dead_hashed(const struct inet_timewait_sock *tw)
-{
-	return !hlist_unhashed(&tw->tw_death_node);
-}
-
-static inline void inet_twsk_dead_node_init(struct inet_timewait_sock *tw)
-{
-	tw->tw_death_node.pprev = NULL;
-}
-
-static inline void __inet_twsk_del_dead_node(struct inet_timewait_sock *tw)
-{
-	__hlist_del(&tw->tw_death_node);
-	inet_twsk_dead_node_init(tw);
-}
-
-static inline int inet_twsk_del_dead_node(struct inet_timewait_sock *tw)
-{
-	if (inet_twsk_dead_hashed(tw)) {
-		__inet_twsk_del_dead_node(tw);
-		return 1;
-	}
-	return 0;
-}
-
-#define inet_twsk_for_each(tw, node, head) \
-	hlist_nulls_for_each_entry(tw, node, head, tw_node)
-
-#define inet_twsk_for_each_inmate(tw, jail) \
-	hlist_for_each_entry(tw, jail, tw_death_node)
-
-#define inet_twsk_for_each_inmate_safe(tw, safe, jail) \
-	hlist_for_each_entry_safe(tw, safe, jail, tw_death_node)
-
 static inline struct inet_timewait_sock *inet_twsk(const struct sock *sk)
 {
 	return (struct inet_timewait_sock *)sk;
@@ -193,16 +106,14 @@ int inet_twsk_bind_unhash(struct inet_timewait_sock *tw,
 			  struct inet_hashinfo *hashinfo);
 
 struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk,
+					   struct inet_timewait_death_row *dr,
 					   const int state);
 
 void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
 			   struct inet_hashinfo *hashinfo);
 
-void inet_twsk_schedule(struct inet_timewait_sock *tw,
-			struct inet_timewait_death_row *twdr,
-			const int timeo, const int timewait_len);
-void inet_twsk_deschedule(struct inet_timewait_sock *tw,
-			  struct inet_timewait_death_row *twdr);
+void inet_twsk_schedule(struct inet_timewait_sock *tw, const int timeo);
+void inet_twsk_deschedule(struct inet_timewait_sock *tw);
 
 void inet_twsk_purge(struct inet_hashinfo *hashinfo,
 		     struct inet_timewait_death_row *twdr, int family);