SQLSERVER排查CPU占用高的情况

现象他说是这几天才出现的，而且在每天的某一个时间段才会出现CPU占用高的情况内存占用不太高，只占用了30个GCPU占用100%



排查方向 一般排查都是用下面的脚本，一般会用到三个视图sys.sysprocesses ,dm_exec_sessions ,dm_exec_requests

1 USE master
2 GO
3 --如果要指定数据库就把注释去掉
4 SELECT * FROM sys.[sysprocesses] WHERE [spid]>50 --AND DB_NAME([dbid])='gposdb'
5 SELECT COUNT(*) FROM [sys].[dm_exec_sessions] WHERE [session_id]>50

看一下当前的数据库用户连接有多少然后使用下面语句看一下各项指标是否正常，是否有阻塞，这个语句选取了前10个最耗CPU时间的会话

1 SELECT TOP 10
2 [session_id],
3 [request_id],
4 [start_time] AS '开始时间',
5 [status] AS '状态',
6 [command] AS '命令',
7 dest.[text] AS 'sql语句',
8 DB_NAME([database_id]) AS '数据库名',
9 [blocking_session_id] AS '正在阻塞其他会话的会话ID',
10 [wait_type] AS '等待资源类型',
11 [wait_time] AS '等待时间',
12 [wait_resource] AS '等待的资源',
13 [reads] AS '物理读次数',
14 [writes] AS '写次数',
15 [logical_reads] AS '逻辑读次数',
16 [row_count] AS '返回结果行数'
17 FROM sys.[dm_exec_requests] AS der
18 CROSS APPLY
19 sys.[dm_exec_sql_text](der.[sql_handle]) AS dest
20 WHERE [session_id]>50 AND DB_NAME(der.[database_id])='gposdb'
21 ORDER BY [cpu_time] DESC

如果想看具体的SQL语句可以执行下面的SQL语句，记得在SSMS里选择以文本格式显示结果

1 --在SSMS里选择以文本格式显示结果
2 SELECT TOP 10
3 dest.[text] AS 'sql语句'
4 FROM sys.[dm_exec_requests] AS der
5 CROSS APPLY
6 sys.[dm_exec_sql_text](der.[sql_handle]) AS dest
7 WHERE [session_id]>50
8 ORDER BY [cpu_time] DESC

模拟了一些耗CPU时间的动作





 还有查看CPU数和user scheduler数和最大工作线程数，检查worker是否用完也可以排查CPU占用情况

1 --查看CPU数和user scheduler数目
2 SELECT cpu_count,scheduler_count FROM sys.dm_os_sys_info
3 --查看最大工作线程数
4 SELECT max_workers_count FROM sys.dm_os_sys_info

查看机器上的所有schedulers包括user 和system
通过下面语句可以看到worker是否用完，当达到最大线程数的时候就要检查blocking了
对照下面这个表
各种CPU和SQLSERVER版本组合自动配置的最大工作线程数
CPU数                 32位计算机                        64位计算机
<=4                     256                                   512
  8                        288                                   576
 16                       352                                   704
 32                       480                                   960

1 SELECT
2 scheduler_address,
3 scheduler_id,
4 cpu_id,
5 status,
6 current_tasks_count,
7 current_workers_count,active_workers_count
8 FROM sys.dm_os_schedulers

 如果SQLSERVER存在要等待的资源，那么执行下面语句就会显示出会话中有多少个worker在等待结合[sys].[dm_os_wait_stats]视图，如果当前SQLSERVER里面没有任何等待资源，那么下面的SQL语句不会显示任何结果

1 SELECT TOP 10
2  [session_id],
3  [request_id],
4  [start_time] AS '开始时间',
5  [status] AS '状态',
6  [command] AS '命令',
7  dest.[text] AS 'sql语句',
8  DB_NAME([database_id]) AS '数据库名',
9  [blocking_session_id] AS '正在阻塞其他会话的会话ID',
10  der.[wait_type] AS '等待资源类型',
11  [wait_time] AS '等待时间',
12  [wait_resource] AS '等待的资源',
13  [dows].[waiting_tasks_count] AS '当前正在进行等待的任务数',
14  [reads] AS '物理读次数',
15  [writes] AS '写次数',
16  [logical_reads] AS '逻辑读次数',
17  [row_count] AS '返回结果行数'
18  FROM sys.[dm_exec_requests] AS der
19  INNER JOIN [sys].[dm_os_wait_stats] AS dows
20  ON der.[wait_type]=[dows].[wait_type]
21  CROSS APPLY
22  sys.[dm_exec_sql_text](der.[sql_handle]) AS dest
23  WHERE [session_id]>50
24  ORDER BY [cpu_time] DESC

比如我当前执行了查询SalesOrderDetail_test表100次，由于表数据非常多，所以SSMS需要把SQLSERVER执行的结果慢慢的取走，造成了ASYNC_NETWORK_IO等待

1 USE [AdventureWorks]
2 GO
3 SELECT * FROM dbo.[SalesOrderDetail_test]
4 GO 100

 问题源头经过排查和这几天的观察情况，确定是某些表缺失索引导致，现在在这些表上增加了索引，问题解决

1 select * from t_AccessControl        --权限控制表权限控制
2 select * from t_GroupAccess            --用户组权限表用户组权限
3 select * from t_GroupAccessType        --用户组权限类表用户组权限类
4 select * from t_ObjectAccess        --对象权限表对象权限
5 select * from t_ObjectAccessType    --对象权限类型表对象权限类型
6 select * from t_ObjectType            --对象类型表对象类型

查询CPU占用高的语句

1 SELECT TOP 10
2    total_worker_time/execution_count AS avg_cpu_cost, plan_handle,
3    execution_count,
4    (SELECT SUBSTRING(text, statement_start_offset/2 + 1,
5       (CASE WHEN statement_end_offset = -1
6          THEN LEN(CONVERT(nvarchar(max), text)) * 2
7          ELSE statement_end_offset
8       END - statement_start_offset)/2)
9    FROM sys.dm_exec_sql_text(sql_handle)) AS query_text
10 FROM sys.dm_exec_query_stats
11 ORDER BY [avg_cpu_cost] DESC

查询缺失索引

1 SELECT
2     DatabaseName = DB_NAME(database_id)
3     ,[Number Indexes Missing] = count(*)
4 FROM sys.dm_db_missing_index_details
5 GROUP BY DB_NAME(database_id)
6 ORDER BY 2 DESC;

1 SELECT  TOP 10
2         [Total Cost]  = ROUND(avg_total_user_cost * avg_user_impact * (user_seeks + user_scans),0)
3         , avg_user_impact
4         , TableName = statement
5         , [EqualityUsage] = equality_columns
6         , [InequalityUsage] = inequality_columns
7         , [Include Cloumns] = included_columns
8 FROM        sys.dm_db_missing_index_groups g
9 INNER JOIN    sys.dm_db_missing_index_group_stats s
10        ON s.group_handle = g.index_group_handle
11 INNER JOIN    sys.dm_db_missing_index_details d
12        ON d.index_handle = g.index_handle
13 ORDER BY [Total Cost] DESC;

定位问题后，新建非聚集索引

1 CREATE NONCLUSTERED INDEX IX_t_AccessControl_F4 ON dbo.t_AccessControl
2 (
3     FObjectType
4 )include([FUserID], [FAccessType], [FAccessMask]) WITH( STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
5 GO
6
7 drop index IX_t_AccessControl_F4 on t_AccessControl

 CPU占用恢复正常

跟踪模板和跟踪文件下载，请使用SQL2008R2 版本：files.cnblogs.com/lyhabc/跟踪模板和trace.rar 总结从多次历史经验来看，如果CPU负载持续很高，但内存和IO都还好的话，这种情况下，首先想到的一定是索引问题，十有八九错不了。注意文章开头贴出的客户机器负载情况图