因生产环境tomcat占用CPU持续过高，负载过高，重启tomcat过于缓慢，参与网上资料，解决tomcat占用CPU过高，重启缓慢问题
1、通过top命令找出占用CPU高的PID
top - 15:52:18 up 93 days, 2:23, 1 user, load average: 9.05, 9.00, 9.17Tasks: 98 total, 1 running, 97 sleeping, 0 stopped, 0 zombieCpu(s): 41.0%us, 59.0%sy, 0.0%ni, 0.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%stMem: 3926224k total, 1070236k used, 2855988k free, 51508k buffersSwap: 6143992k total, 286684k used, 5857308k free, 95404k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 4834 root 20 0 1953m 62m 1848 S 99.2 1.6 28369:16 java 20399 root 20 0 1980m 650m 5724 S 0.3 17.0 6:31.53 java 1 root 20 0 19348 904 632 S 0.0 0.0 0:12.21 init 2 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kthreadd 3 root RT 0 0 0 0 S 0.0 0.0 0:00.00 migration/0 4 root 20 0 0 0 0 S 0.0 0.0 2:50.30 ksoftirqd/0 5 root RT 0 0 0 0 S 0.0 0.0 0:00.00 migration/0 6 root RT 0 0 0 0 S 0.0 0.0 0:11.41 watchdog/0 7 root 20 0 0 0 0 S 0.0 0.0 47:36.80 events/0 8 root 20 0 0 0 0 S 0.0 0.0 0:00.00 cgroup 9 root 20 0 0 0 0 S 0.0 0.0 0:00.00 khelper 10 root 20 0 0 0 0 S 0.0 0.0 0:00.00 netns 11 root 20 0 0 0 0 S 0.0 0.0 0:00.00 async/mgr 12 root 20 0 0 0 0 S 0.0 0.0 0:00.00 pm 13 root 20 0 0 0 0 S 0.0 0.0 0:22.66 sync_supers 14 root 20 0 0 0 0 S 0.0 0.0 0:21.60 bdi-default 15 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kintegrityd/0 16 root 20 0 0 0 0 S 0.0 0.0 1:41.28 kblockd/0 17 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kacpid 18 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kacpi_notify 19 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kacpi_hotplug
2、通过ps aux | grep pid 可以进一步确定是tomcat进程出了问题
3、显示线程列表
[root@tomcat-12 ~]# ps -mp 4834 -o THREAD,tid,timeUSER %CPU PRI SCNT WCHAN USER SYSTEM TID TIMEroot 85.4 - - - - - - 19-16:49:52root 0.0 19 - futex_ - - 4834 00:00:00root 0.0 19 - futex_ - - 4835 00:00:00root 0.0 19 - futex_ - - 4836 00:00:47root 0.0 19 - futex_ - - 4837 00:00:00root 0.0 19 - futex_ - - 4838 00:00:01root 0.0 19 - futex_ - - 4839 00:00:00root 0.0 19 - futex_ - - 4840 00:00:20root 0.0 19 - futex_ - - 4841 00:00:21root 0.0 19 - futex_ - - 4842 00:00:00root 0.0 19 - futex_ - - 4843 00:12:07root 0.0 19 - futex_ - - 4844 00:00:00root 9.4 19 - - - - 4863 2-04:30:24root 9.4 19 - - - - 4871 2-04:30:20root 9.4 19 - - - - 4875 2-04:30:20root 9.4 19 - - - - 4890 2-04:30:20root 9.4 19 - - - - 4893 2-04:30:20root 9.4 19 - - - - 4896 2-04:30:20root 9.4 19 - - - - 4898 2-04:30:20root 9.4 19 - - - - 4904 2-04:30:20root 0.0 19 - futex_ - - 4916 00:00:00root 0.0 19 - futex_ - - 4917 00:00:10root 0.0 19 - futex_ - - 4918 00:00:00root 0.0 19 - futex_ - - 4919 00:00:00root 0.0 19 - futex_ - - 4920 00:00:00root 0.0 19 - futex_ - - 4921 00:00:00root 0.0 19 - futex_ - - 4922 00:00:00root 0.0 19 - futex_ - - 4923 00:00:00root 0.0 19 - futex_ - - 4924 00:00:00root 0.0 19 - futex_ - - 4925 00:00:00root 0.0 19 - futex_ - - 4926 00:00:00root 0.0 19 - futex_ - - 4927 00:00:00root 0.0 19 - futex_ - - 4928 00:00:00root 0.0 19 - futex_ - - 4929 00:00:00root 0.0 19 - futex_ - - 4930 00:00:00root 0.0 19 - futex_ - - 4931 00:00:00root 0.0 19 - futex_ - - 4932 00:00:00root 0.0 19 - futex_ - - 4933 00:00:00root 0.0 19 - futex_ - - 4934 00:00:00root 0.0 19 - futex_ - - 4935 00:00:00root 0.0 19 - futex_ - - 4936 00:00:00root 0.0 19 - futex_ - - 4937 00:00:00root 0.0 19 - futex_ - - 4938 00:00:00root 0.0 19 - futex_ - - 4939 00:00:00root 0.0 19 - futex_ - - 4940 00:00:00root 0.0 19 - futex_ - - 4941 00:00:00root 0.0 19 - futex_ - - 4942 00:00:00root 0.0 19 - futex_ - - 4943 00:00:00root 0.0 19 - futex_ - - 4944 00:00:00root 0.0 19 - futex_ - - 4945 00:00:00root 0.0 19 - futex_ - - 4946 00:00:00root 0.0 19 - futex_ - - 4947 00:00:00root 0.0 19 - futex_ - - 4948 00:00:00root 0.0 19 - futex_ - - 4949 00:00:00root 0.0 19 - futex_ - - 4950 00:00:00root 0.0 19 - futex_ - - 4951 00:00:00root 0.0 19 - futex_ - - 4952 00:00:00root 0.0 19 - futex_ - - 4953 00:00:00root 0.0 19 - futex_ - - 4954 00:00:00root 0.0 19 - futex_ - - 4955 00:00:00root 0.0 19 - futex_ - - 4956 00:00:00root 0.0 19 - futex_ - - 4957 00:00:00root 0.0 19 - futex_ - - 4958 00:00:00root 0.0 19 - futex_ - - 4959 00:00:00root 0.0 19 - futex_ - - 4960 00:00:00root 0.0 19 - futex_ - - 4961 00:00:00root 0.0 19 - futex_ - - 4962 00:00:00root 0.0 19 - futex_ - - 4963 00:00:00root 0.0 19 - futex_ - - 4964 00:00:00root 0.0 19 - futex_ - - 4965 00:00:00root 0.0 19 - futex_ - - 4966 00:00:00root 0.0 19 - futex_ - - 4967 00:00:00root 0.0 19 - futex_ - - 4968 00:00:00root 0.0 19 - futex_ - - 4969 00:00:00root 0.0 19 - futex_ - - 4970 00:00:00root 0.0 19 - futex_ - - 4971 00:00:00root 0.0 19 - futex_ - - 4972 00:00:00root 0.0 19 - futex_ - - 4973 00:00:00root 0.0 19 - futex_ - - 4974 00:00:00root 0.0 19 - futex_ - - 4975 00:00:00root 0.0 19 - futex_ - - 4976 00:00:00root 0.0 19 - futex_ - - 4977 00:00:00root 0.0 19 - futex_ - - 4978 00:00:00root 0.0 19 - futex_ - - 4979 00:00:00root 0.0 19 - futex_ - - 4980 00:00:00root 0.0 19 - futex_ - - 4981 00:00:00root 0.0 19 - futex_ - - 4982 00:00:00root 0.0 19 - futex_ - - 4983 00:00:00root 0.0 19 - futex_ - - 4984 00:00:00root 0.0 19 - futex_ - - 4985 00:00:00root 0.0 19 - futex_ - - 4986 00:00:00root 0.0 19 - futex_ - - 4987 00:00:00root 0.0 19 - futex_ - - 4988 00:00:00root 0.0 19 - futex_ - - 4989 00:00:00root 0.0 19 - futex_ - - 4990 00:00:00root 0.0 19 - futex_ - - 4991 00:00:00root 0.0 19 - futex_ - - 4992 00:00:00root 0.0 19 - futex_ - - 4993 00:00:00root 0.0 19 - futex_ - - 4994 00:00:00root 0.0 19 - futex_ - - 4995 00:00:00root 0.0 19 - futex_ - - 4996 00:00:00root 0.0 19 - futex_ - - 4997 00:00:00root 0.0 19 - futex_ - - 4998 00:00:00root 0.0 19 - futex_ - - 4999 00:00:00root 0.0 19 - futex_ - - 5000 00:00:00root 0.0 19 - futex_ - - 5001 00:00:00root 0.0 19 - futex_ - - 5002 00:00:00root 0.0 19 - futex_ - - 5003 00:00:00root 0.0 19 - futex_ - - 5004 00:00:00root 0.0 19 - futex_ - - 5005 00:00:00root 0.0 19 - futex_ - - 5006 00:00:00root 0.0 19 - futex_ - - 5007 00:00:00root 0.0 19 - futex_ - - 5008 00:00:00root 0.0 19 - futex_ - - 5009 00:00:00root 0.0 19 - futex_ - - 5010 00:00:00root 0.0 19 - futex_ - - 5011 00:00:00root 0.0 19 - futex_ - - 5012 00:00:00root 0.0 19 - futex_ - - 5013 00:00:00root 0.0 19 - futex_ - - 5014 00:00:00root 0.0 19 - futex_ - - 5015 00:00:00root 0.0 19 - futex_ - - 5016 00:00:00root 0.0 19 - futex_ - - 5017 00:00:00root 0.0 19 - futex_ - - 5018 00:00:00root 0.0 19 - futex_ - - 5019 00:00:00root 0.0 19 - futex_ - - 5020 00:00:00root 0.0 19 - futex_ - - 5021 00:00:00root 0.0 19 - futex_ - - 5022 00:00:00root 0.0 19 - futex_ - - 5023 00:00:00root 0.0 19 - futex_ - - 5024 00:00:00root 0.0 19 - futex_ - - 5025 00:00:00root 0.0 19 - futex_ - - 5026 00:00:00root 0.0 19 - futex_ - - 5027 00:00:00root 0.0 19 - futex_ - - 5028 00:00:00root 0.0 19 - futex_ - - 5029 00:00:00root 0.0 19 - futex_ - - 5030 00:00:00root 0.0 19 - futex_ - - 5031 00:00:00root 0.0 19 - futex_ - - 5032 00:00:00root 0.0 19 - futex_ - - 5033 00:00:00root 0.0 19 - futex_ - - 5034 00:00:00root 0.0 19 - futex_ - - 5035 00:00:00root 0.0 19 - futex_ - - 5036 00:00:00root 0.0 19 - futex_ - - 5037 00:00:00root 0.0 19 - futex_ - - 5038 00:00:00root 0.0 19 - futex_ - - 5039 00:00:00root 0.0 19 - futex_ - - 5040 00:00:00root 0.0 19 - futex_ - - 5041 00:00:00root 0.0 19 - futex_ - - 5042 00:00:00root 0.0 19 - futex_ - - 5043 00:00:00root 0.0 19 - futex_ - - 5044 00:00:00root 0.0 19 - futex_ - - 5047 00:00:00root 0.0 19 - futex_ - - 5053 00:00:00root 0.0 19 - futex_ - - 5264 00:00:00root 9.5 19 - - - - 7041 2-04:30:17root 0.0 19 - futex_ - - 7366 00:00:00root 0.0 19 - futex_ - - 7383 00:00:00root 0.0 19 - futex_ - - 7385 00:00:00root 0.0 19 - futex_ - - 7387 00:00:00root 0.0 19 - futex_ - - 7388 00:00:00root 0.0 19 - futex_ - - 7390 00:00:00root 0.0 19 - futex_ - - 7397 00:00:35root 0.0 19 - skb_re - - 24683 00:00:00
通过观察共计7041、4904、4898、4896、4893、4890、4875、4871、4863九个tid占用了CPU
4、打印线程的堆栈信息
[root@tomcat-12 ~]jstack pid | grep tid -A 30
此处不一一列表各tid的堆栈信息了，在其中一个的tid堆栈信息中找到了问题的原因