我在连接到 RDS 实例的 EC2 实例上遇到了性能不佳的问题。此特定实例是在 VPC 出现之前构建的，因此所有流量都流经单个虚拟 NIC。
流量概况维持在 200mbit/s 左右，并在 5-10 秒内爆发至千兆线路的满负荷，这都是入站 MYSQL 流量（对于爆发而言）。相比之下，HTTP 前端流量相当少。
直到最近，突发事件才导致 TCP 拥塞崩溃。我相信这个问题已经解决了，但我确信仍有很多调整机会。我很乐意投入工作，但我希望有网络/整形知识的人能为我指出下一步要做的事情。
以下是我目前所做的：
我将 TCP 拥塞和接收窗口更改为 10（从 3 增加 - Linux 服务器）
我使用静态路由完成了此操作：
ip route show
10.x.x.x/26 dev eth0 proto kernel scope link src 10.x.x.x
169.x.x.x/16 dev eth0 scope link metric 1002
default via 10.x.x.x dev eth0 initcwnd 10 initrwnd 10
这似乎可能缓解了 TCP 拥塞崩溃的最严重情况。
我还使用 tc 对出站 MYSQL 流量进行了优先级设置：
tc qdisc add dev eth0 root handle 1: prio
tc filter add dev eth0 protocol ip parent 1: prio 1 u32 match ip dport 22 0xffff flowid 1:1
tc filter add dev eth0 protocol ip parent 1: prio 1 u32 match ip dport 3306 0xffff flowid 1:1
tc filter add dev eth0 protocol ip parent 1: prio 1 u32 match ip protocol 1 0xff flowid 1:1
这似乎使得应用程序在拥塞期间响应得更好。但是，我们监控与数据库、HTTP 后端和 Java 邮件的连接，它们现在在拥塞期间往往会受到更多影响，这是有道理的。
因此我开始进行 TCP 调优，但由于 HTTP 和 MYSQL 流量非常不同，我不确定下一步应该关注什么。这是 3 天正常运行时间的 netstat -s。我不认为我们在这段时间内出现过崩溃。
netstat -s
Ip:
699681065 total packets received
2 with invalid addresses
0 forwarded
0 incoming packets discarded
699681063 incoming packets delivered
594010173 requests sent out
Icmp:
938 ICMP messages received
19 input ICMP message failed.
ICMP input histogram:
destination unreachable: 885
timeout in transit: 10
redirects: 2
echo requests: 41
58 ICMP messages sent
0 ICMP messages failed
ICMP output histogram:
destination unreachable: 17
echo replies: 41
IcmpMsg:
InType3: 885
InType5: 2
InType8: 41
InType11: 10
OutType0: 41
OutType3: 17
Tcp:
130279 active connections openings
6710364 passive connection openings
32963 failed connection attempts
42347 connection resets received
922 connections established
697481982 segments received
591322387 segments send out
489523 segments retransmited
46 bad segments received.
298575 resets sent
Udp:
2489966 packets received
17 packets to unknown port received.
0 packet receive errors
2490045 packets sent
UdpLite:
TcpExt:
4690 SYN cookies sent
1375 SYN cookies received
139230 invalid SYN cookies received
3720 resets received for embryonic SYN_RECV sockets
5703049 TCP sockets finished time wait in fast timer
6814 packets rejects in established connections because of timestamp
21888759 delayed acks sent
2610 delayed acks further delayed because of locked socket
Quick ack mode was activated 75329 times
6082 times the listen queue of a socket overflowed
6082 SYNs to LISTEN sockets ignored
269160054 packets directly queued to recvmsg prequeue.
4952741078 packets directly received from backlog
34676003473 packets directly received from prequeue
459594123 packets header predicted
39118686 packets header predicted and directly queued to user
65528973 acknowledgments not containing data received
198865300 predicted acknowledgments
124 times recovered from packet loss due to fast retransmit
47018 times recovered from packet loss due to SACK data
1175 bad SACKs received
Detected reordering 1842 times using FACK
Detected reordering 1579 times using SACK
Detected reordering 14 times using reno fast retransmit
Detected reordering 1756 times using time stamp
2698 congestion windows fully recovered
22329 congestion windows partially recovered using Hoe heuristic
TCPDSACKUndo: 25842
11272 congestion windows recovered after partial ack
40247 TCP data loss events
TCPLostRetransmit: 3190
71 timeouts after reno fast retransmit
13024 timeouts after SACK recovery
3134 timeouts in loss state
123997 fast retransmits
19821 forward retransmits
61024 retransmits in slow start
122970 other TCP timeouts
TCPRenoRecoveryFail: 55
3400 sack retransmits failed
35 times receiver scheduled too late for direct processing
72038 DSACKs sent for old packets
149 DSACKs sent for out of order packets
127535 DSACKs received
146 DSACKs for out of order packets received
38801 connections reset due to unexpected data
2113 connections reset due to early user close
14160 connections aborted due to timeout
TCPSACKDiscard: 1131
TCPDSACKIgnoredOld: 981
TCPDSACKIgnoredNoUndo: 12538
TCPSpuriousRTOs: 480
TCPSackShifted: 137435
TCPSackMerged: 314085
TCPSackShiftFallback: 254120
TCPChallengeACK: 3281
TCPSYNChallenge: 8
TCPFromZeroWindowAdv: 16084
TCPToZeroWindowAdv: 16084
TCPWantZeroWindowAdv: 83130
IpExt:
InOctets: 624006853592
OutOctets: 370712171692
下面是我当前的 sysctl：
# Kernel sysctl configuration file for Red Hat Linux
#
# For binary values, 0 is disabled, 1 is enabled. See sysctl(8) and
# sysctl.conf(5) for more details.
# Controls IP packet forwarding
net.ipv4.ip_forward = 0
# Controls source route verification
net.ipv4.conf.default.rp_filter = 1
# Do not accept source routing
net.ipv4.conf.default.accept_source_route = 0
# Controls the System Request debugging functionality of the kernel
kernel.sysrq = 0
# Controls whether core dumps will append the PID to the core filename.
# Useful for debugging multi-threaded applications.
kernel.core_uses_pid = 1
# Controls the use of TCP syncookies
net.ipv4.tcp_syncookies = 1
# Disable netfilter on bridges.
net.bridge.bridge-nf-call-ip6tables = 0
net.bridge.bridge-nf-call-iptables = 0
net.bridge.bridge-nf-call-arptables = 0
# Controls the default maxmimum size of a mesage queue
kernel.msgmnb = 65536
# Controls the maximum size of a message, in bytes
kernel.msgmax = 65536
# Controls the maximum shared segment size, in bytes
kernel.shmmax = 68719476736
# Controls the maximum number of shared memory segments, in pages
kernel.shmall = 4294967296