知识大全 如何解决CPU过度消耗问题

Posted 2022-07-16 索引

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　　问题描述:　　开发人员报告系统运行缓慢 影响用户访问

　　 登陆数据库主机

　　使用vmstat检查 发现CPU资源已经耗尽 大量任务位于运行队列: bash $ vmstat  procs     memory         page          disk        faults     cpu r b w  swap  free  re  mf pi po fr de sr s s s sd   in   sy   cs us sy id                                                                                                                                                                                                                                                               

　　 使用Top命令

　　观察进程CPU耗用 发现没有明显过高CPU使用的进程$ top

last pid: ;  load averages:       : : processes: sleeping running zombie on cpuCPU states: % idle % user % kernel % iowait %swapMemory: M real M free M swap in use M swap free

   PID USERNAME THR PRI NICE  SIZE   RES STATE    TIME    CPU MAND  oracle i         M M run      :   % oracle  oracle i         M M sleep    :   % oracle  oracle i         M M run      :   % oracle  oracle i         M M run      :   % oracle  oracle i         M M run      :   % oracle  oracle i         M M run      :   % oracle  oracle i         M M cpu/     :   % oracle  oracle i         M M run      :   % oracle  oracle i         M M run      :   % oracle  oracle i         M M run      :   % oracle  oracle i         M M run      :   % oracle  oracle i         M M run      :   % oracle  oracle i         M M run      :   % oracle  oracle i         M M run      :   % oracle  oracle i         M M run      :   % oracle

　　 检查进程数量

bash $ ps ef|grep ora|wc l     bash $ ps ef|grep ora|wc l     bash $ ps ef|grep ora|wc l     bash $ ps ef|grep ora|wc l     bash $ ps ef|grep ora|wc l     bash $ ps ef|grep ora|wc l    

　　发现系统存在大量Oracle进程 大约在 左右 而正常情况下Oracle连接数应该在 左右

　　 检查数据库

　　查询v$session_wait获取各进程等待事件SQL> select sid event p p text from v$session_wait;

       SID EVENT                                  P P TEXT        latch free                     E+ address         pmon timer                            duration         rdbms ipc message                     timeout         rdbms ipc message                     timeout        rdbms ipc message                   timeout         rdbms ipc message                  timeout         rdbms ipc message                     timeout       rdbms ipc message                    timeout       rdbms ipc message                    timeout       rdbms ipc message                   timeout       rdbms ipc message                    timeout

       SID EVENT                                  P P TEXT        rdbms ipc message                    timeout         buffer busy waits                      file#        buffer busy waits                      file#       buffer busy waits                      file#       buffer busy waits                      file#       buffer busy waits                      file#       buffer busy waits                      file#       buffer busy waits                      file#       buffer busy waits                      file#       buffer busy waits                      file#       buffer busy waits                      file#

       SID EVENT                                  P P TEXT        buffer busy waits                      file#        buffer busy waits                      file#        db file sequential read                file#        db file sequential read                file#        db file sequential read                file#        db file sequential read                file#        db file sequential read                file#        db file sequential read                file#        db file sequential read                file#        db file sequential read                file#        db file sequential read                file#

       SID EVENT                                  P P TEXT         db file sequential read                file#        db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#

       SID EVENT                                  P P TEXT        db file sequential read                file#       db file sequential read                file#        db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#

       SID EVENT                                  P P TEXT        db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#

       SID EVENT                                  P P TEXT        db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#

       SID EVENT                                  P P TEXT        db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#

       SID EVENT                                  P P TEXT        db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#       db file sequential read                file#        db file sequential read                file#

       SID EVENT                                  P P TEXT         db file sequential read                file#        db file sequential read                file#        db file sequential read                file#        db file sequential read                file#        db file sequential read                file#        db file sequential read                file#        db file sequential read                file#       db file sequential read                file#        db file sequential read                file#        db file sequential read                file#        db file sequential read                file#

       SID EVENT                                  P P TEXT         db file sequential read                file#        db file sequential read                file#        db file scattered read                 file#        db file scattered read                 file#       db file scattered read                 file#       db file scattered read                 file#       db file scattered read                 file#       db file scattered read                 file#       db file scattered read                 file#       db file scattered read                 file#       db file scattered read                 file#

       SID EVENT                                  P P TEXT        db file scattered read                file#       db file scattered read                file#       db file scattered read                file#       db file scattered read                file#        db file scattered read                file#       db file scattered read                file#       db file scattered read                file#       db file scattered read                file#       db file scattered read                file#        db file scattered read                file#         smon timer                          sleep time

       SID EVENT                                  P P TEXT         SQL*Net message to client      driver id       SQL*Net message to client      driver id        SQL*Net more data from client  driver id       SQL*Net more data from client  driver id

rows selected

　　发现存在大量db file scattered read及db file sequential read等待

　　 捕获相关SQL

　　这里用到了我的以下脚本getsqlbysid sql:

SELECT   sql_text    FROM v$sqltext a   WHERE a hash_value = (SELECT sql_hash_value                           FROM v$session b                          WHERE b SID = &sid )ORDER BY piece ASC/ SQL> @getsqlEnter value for sid: old   : where b sid= &sid new   : where b sid=

SQL_TEXT select i vc title i numinfoguid  from  hs_info i where i intenabledflag =   and i intpublishstate =   and i datpublishdate <=sysdate  and i numcatalogguid = order by i datpublishdate desc i numorder desc

SQL> /Enter value for sid: old   : where b sid= &sid new   : where b sid=

SQL_TEXT select i vc title i numinfoguid  from  hs_info i where i intenabledflag =   and i intpublishstate = and i datpublishdate <=sysdate  and i numcatalogguid = order by i datpublishdate desc i numorder desc

SQL> /Enter value for sid: old   : where b sid= &sid new   : where b sid=

SQL_TEXT select i vc title i numinfoguidfrom  hs_info i where i intenabledflag =   and i intpublishstate =   and i datpublishdate <=sysdate  and i numcatalogguid = order by i datpublishdate desc i numorder desc

　　对几个全表扫描进程跟踪以后 得到以上SQL语句 　　以上语句如果良好编码应该使用绑定变量 但是现在这个不是我们关心的

　　使用该应用用户连接 检查其执行计划:

SQL> set autotrace trace explainSQL> select i vc title i numinfoguid      from  hs_info i where i intenabledflag =       and i intpublishstate =   and i datpublishdate <=sysdate      and i numcatalogguid =     order by i datpublishdate desc i numorder desc  ;

Execution Plan        SELECT STATEMENT Optimizer=CHOOSE (Cost= Card= Bytes= )     SORT (ORDER BY) (Cost= Card= Bytes= )     TABLE ACCESS (FULL) OF HS_INFO (Cost= Card= Bytes= )

SQL> select count(*) from hs_info;

  COUNT(*)    

　　该表这里有 万记录 全表扫描已经不再适合

　　检查该表 存在以下索引:

SQL> select index_name index_type  from user_indexes where table_name= HS_INFO ;

INDEX_NAME                     INDEX_TYPE HSIDX_INFO                     FUNCTION BASED NORMALHSIDX_INFO_SEARCHKEY           DOMAINPK_HS_INFO                     NORMAL

　　检查索引键值:

SQL> select index_name column_name from user_ind_columns  where table_name = HS_INFO ;

INDEX_NAME                     COLUMN_NAME HSIDX_INFO                     NUMORDERHSIDX_INFO                     SYS_NC $HSIDX_INFO_SEARCHKEY           VC INDEXWORDSPK_HS_INFO                     NUMINFOGUID

SQL> desc hs_info Name                                  Null?    Type   NUMINFOGUID                         NOT NULL NUMBER( ) NUMCATALOGGUID                      NOT NULL NUMBER( ) INTTEXTTYPE                         NOT NULL NUMBER( ) VC TITLE                            NOT NULL VARCHAR ( ) VC AUTHOR                                    VARCHAR ( ) NUMPREVINFOGUID                              NUMBER( ) NUMNEXTINFOGUID                              NUMBER( ) NUMORDER                            NOT NULL NUMBER( ) DATPUBLISHDATE                      NOT NULL DATE INTPUBLISHSTATE                     NOT NULL NUMBER( ) VC PUBLISHERID                               VARCHAR ( ) VC INDEXWORDS                                VARCHAR ( ) VC WAPPREVPATH                               VARCHAR ( ) VC WEBPREVPATH                               VARCHAR ( ) VC WAP PREVPATH                              VARCHAR ( ) NUMVISITED                          NOT NULL NUMBER( ) INTENABLEDFLAG                      NOT NULL NUMBER( ) DATCREATETIME                       NOT NULL DATE DATMODIFYTIME                       NOT NULL DATE VC NOTES                                     VARCHAR ( ) INTINFOTYPE                         NOT NULL NUMBER( ) VC PRIZEFLAG                                 VARCHAR ( ) VC DESC                                      VARCHAR ( )

　　 决定创建新的索引以消除全表扫描SQL> create index hs_info_NUMCATALOGGUID on hs_info(NUMCATALOGGUID);

Index created

SQL> set autotrace trace explainSQL> select i vc title i numinfoguid      from  hs_info i where i intenabledflag =       and i intpublishstate =   and i datpublishdate <=sysdate      and i numcatalogguid =     order by i datpublishdate desc i numorder desc ;

Execution Plan    SELECT STATEMENT Optimizer=CHOOSE (Cost= Card= Bytes= ) SORT (ORDER BY) (Cost= Card= Bytes= ) TABLE ACCESS (BY INDEX ROWID) OF HS_INFO (Cost= Card= Bytes= ) INDEX (RANGE SCAN)OF HS_INFO_NUMCATALOGGUID (NON UNIQUE)(Cost= Card= )

　　 观察系统状况

　　原大量等待消失

SQL> select sid event p p text from v$session_wait where event not like SQL% ;

       SID EVENT                                  P P TEXT          pmon timer                            duration         rdbms ipc message                     timeout         rdbms ipc message                     timeout         rdbms ipc message                  timeout        rdbms ipc message                    timeout       rdbms ipc message                    timeout       rdbms ipc message                   timeout       rdbms ipc message                    timeout        rdbms ipc message                    timeout        rdbms ipc message                   timeout         rdbms ipc message                     timeout

       SID EVENT                                  P P TEXT        db file sequential read                file#       db file sequential read                file#        db file scattered read                 file#         smon timer                            sleep time

rows selected

　　持续观察的CPU使用情况 bash $ vmstat  procs     memory            page            disk          faults      cpu r b w   swap  free  re  mf pi po fr de sr s s s sd   in   sy   cs us sy id                                                                                                                                                                                          以上为创建索引之前部分 以下为创建索引之后部分 CPU使用率恢复正常  procs     memory            page            disk          faults      cpu r b w   swap  free  re  mf pi po fr de sr s s s sd   in   sy   cs us sy id                                                                                                                                                                                                                                                                                           

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