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>
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 2088fdc..63d6311 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -34,18 +34,7 @@
struct inet_timewait_death_row tcp_death_row = {
.sysctl_max_tw_buckets = NR_FILE * 2,
- .period = TCP_TIMEWAIT_LEN / INET_TWDR_TWKILL_SLOTS,
- .death_lock = __SPIN_LOCK_UNLOCKED(tcp_death_row.death_lock),
.hashinfo = &tcp_hashinfo,
- .tw_timer = TIMER_INITIALIZER(inet_twdr_hangman, 0,
- (unsigned long)&tcp_death_row),
- .twkill_work = __WORK_INITIALIZER(tcp_death_row.twkill_work,
- inet_twdr_twkill_work),
-/* Short-time timewait calendar */
-
- .twcal_hand = -1,
- .twcal_timer = TIMER_INITIALIZER(inet_twdr_twcal_tick, 0,
- (unsigned long)&tcp_death_row),
};
EXPORT_SYMBOL_GPL(tcp_death_row);
@@ -158,7 +147,7 @@
if (!th->fin ||
TCP_SKB_CB(skb)->end_seq != tcptw->tw_rcv_nxt + 1) {
kill_with_rst:
- inet_twsk_deschedule(tw, &tcp_death_row);
+ inet_twsk_deschedule(tw);
inet_twsk_put(tw);
return TCP_TW_RST;
}
@@ -174,11 +163,9 @@
if (tcp_death_row.sysctl_tw_recycle &&
tcptw->tw_ts_recent_stamp &&
tcp_tw_remember_stamp(tw))
- inet_twsk_schedule(tw, &tcp_death_row, tw->tw_timeout,
- TCP_TIMEWAIT_LEN);
+ inet_twsk_schedule(tw, tw->tw_timeout);
else
- inet_twsk_schedule(tw, &tcp_death_row, TCP_TIMEWAIT_LEN,
- TCP_TIMEWAIT_LEN);
+ inet_twsk_schedule(tw, TCP_TIMEWAIT_LEN);
return TCP_TW_ACK;
}
@@ -211,13 +198,12 @@
*/
if (sysctl_tcp_rfc1337 == 0) {
kill:
- inet_twsk_deschedule(tw, &tcp_death_row);
+ inet_twsk_deschedule(tw);
inet_twsk_put(tw);
return TCP_TW_SUCCESS;
}
}
- inet_twsk_schedule(tw, &tcp_death_row, TCP_TIMEWAIT_LEN,
- TCP_TIMEWAIT_LEN);
+ inet_twsk_schedule(tw, TCP_TIMEWAIT_LEN);
if (tmp_opt.saw_tstamp) {
tcptw->tw_ts_recent = tmp_opt.rcv_tsval;
@@ -267,8 +253,7 @@
* Do not reschedule in the last case.
*/
if (paws_reject || th->ack)
- inet_twsk_schedule(tw, &tcp_death_row, TCP_TIMEWAIT_LEN,
- TCP_TIMEWAIT_LEN);
+ inet_twsk_schedule(tw, TCP_TIMEWAIT_LEN);
return tcp_timewait_check_oow_rate_limit(
tw, skb, LINUX_MIB_TCPACKSKIPPEDTIMEWAIT);
@@ -283,16 +268,15 @@
*/
void tcp_time_wait(struct sock *sk, int state, int timeo)
{
- struct inet_timewait_sock *tw = NULL;
const struct inet_connection_sock *icsk = inet_csk(sk);
const struct tcp_sock *tp = tcp_sk(sk);
+ struct inet_timewait_sock *tw;
bool recycle_ok = false;
if (tcp_death_row.sysctl_tw_recycle && tp->rx_opt.ts_recent_stamp)
recycle_ok = tcp_remember_stamp(sk);
- if (tcp_death_row.tw_count < tcp_death_row.sysctl_max_tw_buckets)
- tw = inet_twsk_alloc(sk, state);
+ tw = inet_twsk_alloc(sk, &tcp_death_row, state);
if (tw) {
struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
@@ -355,8 +339,7 @@
timeo = TCP_TIMEWAIT_LEN;
}
- inet_twsk_schedule(tw, &tcp_death_row, timeo,
- TCP_TIMEWAIT_LEN);
+ inet_twsk_schedule(tw, timeo);
inet_twsk_put(tw);
} else {
/* Sorry, if we're out of memory, just CLOSE this