[root@localhost ~]# tcpdump -i lo -s 1500 port 9000
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on lo, link-type EN10MB (Ethernet), capture size 1500 bytes
11:14:03.711955 IP localhost.localdomain.50708 > localhost.localdomain.9000: S 2207544028:2207544028(0) win 32767 <mss 16396,sackOK,timestamp 3491628977 0,nop,wscale 7>
11:14:03.712218 IP localhost.localdomain.9000 > localhost.localdomain.50708: S 2221134347:2221134347(0) ack 2207544029 win 32767 <mss 16396,sackOK,timestamp 3491628977 3491628977,nop,wscale 7>
11:14:03.712241 IP localhost.localdomain.50708 > localhost.localdomain.9000: . ack 1 win 256 <nop,nop,timestamp 3491628977 3491628977>
11:14:03.712257 IP localhost.localdomain.50708 > localhost.localdomain.9000: P 1:1257(1256) ack 1 win 256 <nop,nop,timestamp 3491628977 3491628977>
11:14:03.712273 IP localhost.localdomain.9000 > localhost.localdomain.50708: . ack 1257 win 256 <nop,nop,timestamp 3491628977 3491628977>
11:14:03.711969 IP localhost.localdomain.9000 > localhost.localdomain.50708: P 1:2985(2984) ack 1257 win 256 <nop,nop,timestamp 3491628978 3491628977>
11:14:03.711980 IP localhost.localdomain.50708 > localhost.localdomain.9000: . ack 2985 win 303 <nop,nop,timestamp 3491628978 3491628978>
11:14:05.738632 IP localhost.localdomain.50708 > localhost.localdomain.9000: P 1257:2513(1256) ack 2985 win 303 <nop,nop,timestamp 3491631005 3491628978>
11:14:05.738832 IP localhost.localdomain.9000 > localhost.localdomain.50708: P 2985:5969(2984) ack 2513 win 256 <nop,nop,timestamp 3491631005 3491631005>
11:14:05.738848 IP localhost.localdomain.50708 > localhost.localdomain.9000: . ack 5969 win 303 <nop,nop,timestamp 3491631005 3491631005>
11:14:06.901924 IP localhost.localdomain.50708 > localhost.localdomain.9000: P 2513:3769(1256) ack 5969 win 303 <nop,nop,timestamp 3491632168 3491631005>
11:14:06.902098 IP localhost.localdomain.9000 > localhost.localdomain.50708: P 5969:8953(2984) ack 3769 win 256 <nop,nop,timestamp 3491632168 3491632168>
11:14:06.902110 IP localhost.localdomain.50708 > localhost.localdomain.9000: . ack 8953 win 303 <nop,nop,timestamp 3491632168 3491632168>
11:14:07.570211 IP localhost.localdomain.50708 > localhost.localdomain.9000: P 3769:5025(1256) ack 8953 win 303 <nop,nop,timestamp 3491632836 3491632168>
11:14:07.570387 IP localhost.localdomain.9000 > localhost.localdomain.50708: P 8953:11937(2984) ack 5025 win 256 <nop,nop,timestamp 3491632837 3491632836>
11:14:07.570399 IP localhost.localdomain.50708 > localhost.localdomain.9000: . ack 11937 win 303 <nop,nop,timestamp 3491632837 3491632837>
11:14:08.202399 IP localhost.localdomain.50708 > localhost.localdomain.9000: P 5025:6281(1256) ack 11937 win 303 <nop,nop,timestamp 3491633469 3491632837>
11:14:08.202473 IP localhost.localdomain.9000 > localhost.localdomain.50708: P 11937:14921(2984) ack 6281 win 256 <nop,nop,timestamp 3491633469 3491633469>
11:14:08.202483 IP localhost.localdomain.50708 > localhost.localdomain.9000: . ack 14921 win 303 <nop,nop,timestamp 3491633469 3491633469>
11:14:09.475039 IP localhost.localdomain.50708 > localhost.localdomain.9000: P 6281:7537(1256) ack 14921 win 303 <nop,nop,timestamp 3491634742 3491633469>
11:14:09.475277 IP localhost.localdomain.9000 > localhost.localdomain.50708: P 14921:17905(2984) ack 7537 win 256 <nop,nop,timestamp 3491634742 3491634742>
11:14:09.475291 IP localhost.localdomain.50708 > localhost.localdomain.9000: . ack 17905 win 303 <nop,nop,timestamp 3491634742 3491634742>
11:14:10.082268 IP localhost.localdomain.50708 > localhost.localdomain.9000: P 7537:8793(1256) ack 17905 win 303 <nop,nop,timestamp 3491635349 3491634742>
11:14:10.082512 IP localhost.localdomain.9000 > localhost.localdomain.50708: P 17905:20889(2984) ack 8793 win 256 <nop,nop,timestamp 3491635349 3491635349>
11:14:10.082522 IP localhost.localdomain.50708 > localhost.localdomain.9000: . ack 20889 win 303 <nop,nop,timestamp 3491635349 3491635349>
11:14:10.818134 IP localhost.localdomain.50708 > localhost.localdomain.9000: P 8793:10049(1256) ack 20889 win 303 <nop,nop,timestamp 3491636085 3491635349>
11:14:10.818252 IP localhost.localdomain.9000 > localhost.localdomain.50708: P 20889:23873(2984) ack 10049 win 256 <nop,nop,timestamp 3491636085 3491636085>
11:14:10.818263 IP localhost.localdomain.50708 > localhost.localdomain.9000: . ack 23873 win 303 <nop,nop,timestamp 3491636085 3491636085>
11:14:11.506168 IP localhost.localdomain.50711 > localhost.localdomain.9000: S 2218187766:2218187766(0) win 32767 <mss 16396,sackOK,timestamp 3491636773 0,nop,wscale 7>
11:14:11.506191 IP localhost.localdomain.9000 > localhost.localdomain.50711: S 2224663648:2224663648(0) ack 2218187767 win 32767 <mss 16396,sackOK,timestamp 3491636773 3491636773,nop,wscale 7>
11:14:11.506205 IP localhost.localdomain.50711 > localhost.localdomain.9000: . ack 1 win 256 <nop,nop,timestamp 3491636773 3491636773>
11:14:11.506318 IP localhost.localdomain.50711 > localhost.localdomain.9000: P 1:1257(1256) ack 1 win 256 <nop,nop,timestamp 3491636773 3491636773>
11:14:11.506329 IP localhost.localdomain.9000 > localhost.localdomain.50711: . ack 1257 win 256 <nop,nop,timestamp 3491636773 3491636773>
11:15:11.506325 IP localhost.localdomain.50711 > localhost.localdomain.9000: F 1257:1257(0) ack 1 win 256 <nop,nop,timestamp 3491696782 3491636773>
11:15:11.546176 IP localhost.localdomain.9000 > localhost.localdomain.50711: . ack 1258 win 256 <nop,nop,timestamp 3491696822 3491696782>
上面我启动了两个nginx工作进程，
发现在第一个进程执行保持keepalive是没有问题的，一旦第二个进程取得了处理权后，就歇菜了，后端fastcgi就没有响应了，导致客户端迟迟没有响应
我们用strace进行查看fastcgi在干吗？