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authorEric Dumazet <edumazet@google.com>2015-04-12 18:51:09 -0700
committerDavid S. Miller <davem@davemloft.net>2015-04-13 16:40:05 -0400
commit789f558cfb3680aeb52de137418637f6b04b7d22 (patch)
tree0031c54a2fe41480ed509ba140a1c12ecad075a6 /net/ipv4/proc.c
parent20a1d16526b79c76cd45e29cb637aec1d43c41de (diff)
downloadlinux-789f558cfb3680aeb52de137418637f6b04b7d22.tar.bz2
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/ipv4/proc.c')
-rw-r--r--net/ipv4/proc.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index d8953ef0770c..e1f3b911dd1e 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -63,7 +63,7 @@ static int sockstat_seq_show(struct seq_file *seq, void *v)
socket_seq_show(seq);
seq_printf(seq, "TCP: inuse %d orphan %d tw %d alloc %d mem %ld\n",
sock_prot_inuse_get(net, &tcp_prot), orphans,
- tcp_death_row.tw_count, sockets,
+ atomic_read(&tcp_death_row.tw_count), sockets,
proto_memory_allocated(&tcp_prot));
seq_printf(seq, "UDP: inuse %d mem %ld\n",
sock_prot_inuse_get(net, &udp_prot),