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| author | Eric Dumazet <edumazet@google.com> | 2015-04-12 18:51:09 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2015-04-13 16:40:05 -0400 |
| commit | 789f558cfb3680aeb52de137418637f6b04b7d22 (patch) | |
| tree | 0031c54a2fe41480ed509ba140a1c12ecad075a6 /net/dccp | |
| parent | 20a1d16526b79c76cd45e29cb637aec1d43c41de (diff) | |
| download | lwn-789f558cfb3680aeb52de137418637f6b04b7d22.tar.gz lwn-789f558cfb3680aeb52de137418637f6b04b7d22.zip | |
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>
Diffstat (limited to 'net/dccp')
| -rw-r--r-- | net/dccp/minisocks.c | 19 |
1 files changed, 3 insertions, 16 deletions
diff --git a/net/dccp/minisocks.c b/net/dccp/minisocks.c index 332f7d6d9942..5f566663e47f 100644 --- a/net/dccp/minisocks.c +++ b/net/dccp/minisocks.c @@ -27,28 +27,16 @@ struct inet_timewait_death_row dccp_death_row = { .sysctl_max_tw_buckets = NR_FILE * 2, - .period = DCCP_TIMEWAIT_LEN / INET_TWDR_TWKILL_SLOTS, - .death_lock = __SPIN_LOCK_UNLOCKED(dccp_death_row.death_lock), .hashinfo = &dccp_hashinfo, - .tw_timer = TIMER_INITIALIZER(inet_twdr_hangman, 0, - (unsigned long)&dccp_death_row), - .twkill_work = __WORK_INITIALIZER(dccp_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)&dccp_death_row), }; EXPORT_SYMBOL_GPL(dccp_death_row); void dccp_time_wait(struct sock *sk, int state, int timeo) { - struct inet_timewait_sock *tw = NULL; + struct inet_timewait_sock *tw; - if (dccp_death_row.tw_count < dccp_death_row.sysctl_max_tw_buckets) - tw = inet_twsk_alloc(sk, state); + tw = inet_twsk_alloc(sk, &dccp_death_row, state); if (tw != NULL) { const struct inet_connection_sock *icsk = inet_csk(sk); @@ -71,8 +59,7 @@ void dccp_time_wait(struct sock *sk, int state, int timeo) if (state == DCCP_TIME_WAIT) timeo = DCCP_TIMEWAIT_LEN; - inet_twsk_schedule(tw, &dccp_death_row, timeo, - DCCP_TIMEWAIT_LEN); + inet_twsk_schedule(tw, timeo); inet_twsk_put(tw); } else { /* Sorry, if we're out of memory, just CLOSE this |