今天发生数据库查询返回一半的json数据，之前以为设置c3p0的maxIdleTime为大值会解决问题，没想到问题依旧存在。
用top命令分析一下java内存:
[101@G3_101 bin]$ top
top - 15:58:38 up 66 days, 6:07, 2 users, load average: 0.00, 0.00, 0.00
Tasks: 119 total, 1 running, 118 sleeping, 0 stopped, 0 zombie
Cpu(s): 0.3%us, 0.2%sy, 0.0%ni, 99.5%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 3924684k total, 1378960k used, 2545724k free, 169944k buffers
Swap: 4194296k total, 23792k used, 4170504k free, 343196k cached
PID USER PR NI VIRT RES SHR S %cpu %mem TIME+ COMMAND
1661 mysql 20 0 1178m 117m 3456 S 0.3 3.1 70:42.33 mysqld
24483 101 20 0 2237m 534m 12m S 0.3 13.9 1:00.40 java
24531 101 20 0 15028 1324 1004 R 0.3 0.0 0:01.20 top
1 root 20 0 19232 1348 1192 S 0.0 0.0 0:01.12 init
从分析得出，系统内存足够多，java进程VIRT 2237m虚拟内存，VIRT=SWAP+RES , 闲置虚拟内存还有534m 。
SHR表示共享内存大小，12m。从这些判断java虚拟机不存在，内存使用率占13.9%，不存在内存不够的情况。
分析mysql 虚拟内存总大小为1178m,闲置虚拟内存117.共共享内存3456。内存使用率占3.1%,不存在内存不够的情况。
还爆出如下异常：
[org.springframework.web.servlet.DispatcherServlet]DispatcherServlet with name 'springMvc' processing GET request for [/nstatsback/101admin/teaching/teaching.do] [org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping]Mapping [/101admin/teaching/teaching.do] to HandlerExecutionChain with handler [com.chinaedu.nstats.controller.NStatsController@47217048] and 1 interceptor [org.springframework.web.servlet.DispatcherServlet]Last-Modified value for [/nstatsback/101admin/teaching/teaching.do] is: -1 [org.springframework.web.bind.annotation.support.HandlerMethodInvoker]Invoking request handler method: public void com.chinaedu.nstats.controller.NStatsController.teaching(java.lang.String,java.lang.String,javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse) throws java.io.IOException java.lang.NullPointerException [org.springframework.jdbc.datasource.DataSourceUtils]Fetching JDBC Connection from DataSource [com.mchange.v2.resourcepool.BasicResourcePool]trace com.mchange.v2.resourcepool.BasicResourcePool@75b67ac7 [managed: 8, unused: 7, excluded: 0] (e.g. com.mchan ge.v2.c3p0.impl.NewPooledConnection@3c7173bf) [org.springframework.jdbc.datasource.DataSourceUtils]Returning JDBC Connection to DataSource [com.mchange.v2.resourcepool.BasicResourcePool]trace com.mchange.v2.resourcepool.BasicResourcePool@75b67ac7 [managed: 8, unused: 7, excluded: 0] (e.g. com.mchan.v2.c3p0.impl.NewPooledConnection@3c7173bf) [org.springframework.jdbc.datasource.DataSourceUtils]Fetching JDBC Connection from DataSource [com.mchange.v2.resourcepool.BasicResourcePool]trace com.mchange.v2.resourcepool.BasicResourcePool@75b67ac7 [managed: 8, unused: 7, excluded: 0] (e.g. com.mchange.v2.c3p0.impl.NewPooledConnection@3c7173bf) [org.springframework.jdbc.datasource.DataSourceUtils]Returning JDBC Connection to DataSource [com.mchange.v2.resourcepool.BasicResourcePool]trace com.mchange.v2.resourcepool.BasicResourcePool@75b67ac7 [managed: 8, unused: 7, excluded: 0] (e.g. com.mchange.v2.c3p0.impl.NewPooledConnection@3c7173bf) [com.mchange.v2.c3p0.impl.NewProxyConnection]com.mchange.v2.c3p0.impl.NewProxyConnection@456e5122: close() called more than once. [org.springframework.web.servlet.DispatcherServlet]Null ModelAndView returned toDispatcherServlet with name 'springMvc': assuming HandlerAdapter completed request handling [org.springframework.web.servlet.DispatcherServlet]Successfully completed request [com.mchange.v2.resourcepool.BasicResourcePool]Refurbishing idle resources - Mon May 04 16:16:30 CST 2015 [com.mchange.v2.resourcepool.BasicResourcePool@75b67ac7] [com.mchange.v2.resourcepool.BasicResourcePool]trace com.mchange.v2.resourcepool.BasicResourcePool@75b67ac7 [managed: 8, unused: 8, excluded: 0] (e.g. com.mchange.v2.c3p0.impl.NewPooledConnection@3c7173bf) [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@3b27e6c4] on IDLE CHECK. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@704f8e8e] on IDLE CHECK. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@38a2aba4] on IDLE CHECK. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@704f8e8e] on IDLE CHECK has SUCCEEDED. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@498538c1] on IDLE CHECK. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@3b27e6c4] on IDLE CHECK has SUCCEEDED. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@1295eede] on IDLE CHECK. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@38a2aba4] on IDLE CHECK has SUCCEEDED. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@34e920c8] on IDLE CHECK. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@498538c1] on IDLE CHECK has SUCCEEDED. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@5848ddac] on IDLE CHECK. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@1295eede] on IDLE CHECK has SUCCEEDED. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@403d1c18] on IDLE CHECK. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@34e920c8] on IDLE CHECK has SUCCEEDED. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@5848ddac] on IDLE CHECK has SUCCEEDED. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@403d1c18] on IDLE CHECK has SUCCEEDED. [com.mchange.v2.resourcepool.BasicResourcePool]Refurbishing idle resources - Mon May 04 16:17:30 CST 2015 [com.mchange.v2.resourcepool.BasicResourcePool@75b67ac7] [com.mchange.v2.resourcepool.BasicResourcePool]trace com.mchange.v2.resourcepool.BasicResourcePool@75b67ac7 [managed: 8, unused: 8, excluded: 0] (e.g. com.mchange.v2.c3p0.impl.NewPooledConnection@3c7173bf) [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@3b27e6c4] on IDLE CHECK. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@38a2aba4] on IDLE CHECK. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@704f8e8e] on IDLE CHECK. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@38a2aba4] on IDLE CHECK has SUCCEEDED. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@704f8e8e] on IDLE CHECK has SUCCEEDED. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@498538c1] on IDLE CHECK. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@3b27e6c4] on IDLE CHECK has SUCCEEDED. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@34e920c8] on IDLE CHECK. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@1295eede] on IDLE CHECK. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@498538c1] on IDLE CHECK has SUCCEEDED. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@5848ddac] on IDLE CHECK. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@34e920c8] on IDLE CHECK has SUCCEEDED. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@403d1c18] on IDLE CHECK. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@5848ddac] on IDLE CHECK has SUCCEEDED. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@1295eede] on IDLE CHECK has SUCCEEDED. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@403d1c18] on IDLE CHECK has SUCCEEDED. loginFilter end update gm_login_log SET user_id =?, u_num =?, ip =?, class_id =?, semester_code =?, login_time =?, school_id =?, create_time =?, create_user =?, modify_time =?, modify_user =?, delete_flag =?, school_code =?, check_time =?, stay_time =?, role_code =? where id=? [com.mchange.v2.resourcepool.BasicResourcePool]Checking for expired resources - Mon May 04 16:18:00 CST 2015 [com.mchange.v2.resourcepool.BasicResourcePool@75b67ac7] [com.mchange.v2.resourcepool.BasicResourcePool]BEGIN check for expired resources. [com.mchange.v2.resourcepool.BasicResourcePool@75b67ac7] [com.mchange.v2.resourcepool.BasicResourcePool]FINISHED check for expired resources. [com.mchange.v2.resourcepool.BasicResourcePool@75b67ac7] [com.mchange.v2.resourcepool.BasicResourcePool]Refurbishing idle resources - Mon May 04 16:18:30 CST 2015 [com.mchange.v2.resourcepool.BasicResourcePool@75b67ac7] [com.mchange.v2.resourcepool.BasicResourcePool]trace com.mchange.v2.resourcepool.BasicResourcePool@75b67ac7 [managed: 8, unused: 8, excluded: 0] (e.g. com.mchange.v2.c3p0.impl.NewPooledConnection@3c7173bf) [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@3b27e6c4] on IDLE CHECK. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@38a2aba4] on IDLE CHECK. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@704f8e8e] on IDLE CHECK. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@704f8e8e] on IDLE CHECK has SUCCEEDED. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@498538c1] on IDLE CHECK. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@3b27e6c4] on IDLE CHECK has SUCCEEDED. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@1295eede] on IDLE CHECK. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@38a2aba4] on IDLE CHECK has SUCCEEDED. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@34e920c8] on IDLE CHECK. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@498538c1] on IDLE CHECK has SUCCEEDED. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@5848ddac] on IDLE CHECK. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@1295eede] on IDLE CHECK has SUCCEEDED. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Testing PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@403d1c18] on IDLE CHECK. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@5848ddac] on IDLE CHECK has SUCCEEDED. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@34e920c8] on IDLE CHECK has SUCCEEDED. [com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool]Test of PooledConnection [com.mchange.v2.c3p0.impl.NewPooledConnection@403d1c18] on IDLE CHECK has SUCCEEDED.
更多linux top命令参考文章http://www.jb51.net/LINUXjishu/34604.html
Linux系统的物理cpu数、核数、逻辑cpu个数查看
# 总核数 = 物理CPU个数 X 每颗物理CPU的核数 # 总逻辑CPU数 = 物理CPU个数 X 每颗物理CPU的核数 X 超线程数 # 查看物理CPU个数 cat /proc/cpuinfo| grep "physical id"| sort| uniq| wc -l # 查看每个物理CPU中core的个数(即核数) cat /proc/cpuinfo| grep "cpu cores"| uniq # 查看逻辑CPU的个数 cat /proc/cpuinfo| grep "processor"| wc -l # 查看CPU信息（型号） cat /proc/cpuinfo | grep name | cut -f2 -d: | uniq -c