I have a VSP (centos6.1 64bit) with 4gb ram.
It always runs well, but in recent few days, the server become slowly. open a small css file need 22 seconds(2kb). tested in home/office/phone with (IE,chrome,safari,firefox). see in firebug networking
DNS Lookup 4 ms
Connecting 21.18 s
Sending 1 ms
Waiting 115 ms
Receiving 9 ms
The connection cost 21.18 seconds
I have checked all the log file, there have no error. top commond, still have free memory.
top - 00:23:15 up 8 days, 3:57, 1 user, load average: 3.60, 3.42, 3.83
Tasks: 221 total, 4 running, 217 sleeping, 0 stopped, 0 zombie
Cpu(s): 19.3%us, 3.2%sy, 0.0%ni, 76.1%id, 1.4%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 4194304k total, 3247724k used, 946580k free, 0k buffers
Swap: 0k total, 0k used, 0k free, 0k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
32357 mysql 15 0 3710m 835m 6268 S 34.5 20.4 39:14.40 mysqld
9780 apache 15 0 442m 59m 12m S 33.2 1.4 0:05.69 httpd
9842 apache 15 0 403m 26m 10m S 16.9 0.7 0:01.23 httpd
9847 apache 15 0 412m 45m 22m R 15.3 1.1 0:01.00 httpd
9834 apache 15 0 426m 46m 11m R 13.0 1.1 0:02.22 httpd
9891 apache 15 0 407m 43m 19m S 8.0 1.1 0:00.33 httpd
9845 apache 15 0 414m 51m 24m S 6.0 1.3 0:01.53 httpd
9827 apache 15 0 402m 28m 11m S 3.3 0.7 0:02.69 httpd
9768 apache 16 0 414m 51m 24m S 3.0 1.3 0:06.51 httpd
9889 root 15 0 211m 12m 8160 S 2.7 0.3 0:00.32 php
9702 apache 15 0 415m 55m 26m S 1.7 1.4 0:10.67 httpd
9844 apache 15 0 413m 47m 21m S 1.7 1.2 0:01.21 httpd
9697 apache 15 0 414m 51m 24m S 1.3 1.3 0:11.05 httpd
9778 apache 15 0 414m 53m 25m S 1.3 1.3 0:05.38 httpd
9772 apache 15 0 414m 51m 23m R 0.7 1.3 0:05.04 httpd
9823 apache 15 0 415m 50m 23m S 0.7 1.2 0:03.97 httpd
9837 apache 15 0 402m 27m 11m S 0.3 0.7 0:01.04 httpd
Then, how to check where is the problem and fixed it? I haven't change and config files in these days. Thanks.
Best Answer
I have heard that in case of broken IPv6 connectivity, Windows will wait exactly 21 seconds before falling back to IPv4. And the symptom of that failure should match exactly what you see, namely a long delay on establishing a connection.
What can be done about this problem?