SQLSERVER排查CPU佔用高的情況

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SQLSERVER排查CPU佔用高的情況

今天中午，有朋友叫我幫他看一下資料庫，作業系統是Windows2008R2 ,資料庫是SQL2008R2 64位

64G記憶體，16核CPU

硬體設定還是比較高的，他說伺服器啟動並執行是金蝶K3軟體，資料庫執行個體裡有多個資料庫

他說是這幾天才出現的，而且在每天的某一個時間段才會出現CPU佔用高的情況

記憶體佔用也很高，佔用了30個G

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一般排查都是用下面的指令碼，一般會用到三個視圖sys.sysprocesses ,dm_exec_sessions ,dm_exec_requests

1 USE master2 GO3 --如果要指定資料庫就把注釋去掉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

看一下當前的資料庫使用者串連有多少

然後使用下面語句看一下各項指標是否正常，是否有阻塞，這個語句選取了前10個最耗CPU時間的會話

 1 SELECT TOP 10 2 [session_id], 3 [request_id], 4 [start_time] AS ‘開始時間‘, 5 [status] AS ‘狀態‘, 6 [command] AS ‘命令‘, 7 dest.[text] AS ‘sql語句‘,  8 DB_NAME([database_id]) AS ‘資料庫名‘, 9 [blocking_session_id] AS ‘正在阻塞其他會話的會話ID‘,10 [wait_type] AS ‘等待資源類型‘,11 [wait_time] AS ‘等待時間‘,12 [wait_resource] AS ‘等待的資源‘,13 [reads] AS ‘物理讀次數‘,14 [writes] AS ‘寫次數‘,15 [logical_reads] AS ‘邏輯讀次數‘,16 [row_count] AS ‘返回結果行數‘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

如果想看具體的SQL語句可以執行下面的SQL語句，記得在SSMS裡選擇以文字格式設定顯示結果

1 --在SSMS裡選擇以文字格式設定顯示結果2 SELECT TOP 10 3 dest.[text] AS ‘sql語句‘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

類比了一些耗CPU時間的動作

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還有查看CPU數和user scheduler數和最大背景工作執行緒數，檢查worker是否用完也可以排查CPU佔用情況

1 --查看CPU數和user scheduler數目2 SELECT cpu_count,scheduler_count FROM sys.dm_os_sys_info3 --查看最大背景工作執行緒數4 SELECT max_workers_count FROM sys.dm_os_sys_info

查看機器上的所有schedulers包括user 和system
通過下面語句可以看到worker是否用完，當達到最大線程數的時候就要檢查blocking了

對照下面這個表
各種CPU和SQLSERVER版本組合自動設定的最大背景工作執行緒數
CPU數                 32位電腦                        64位電腦
<=4                     256                                   512
  8                        288                                   576
 16                       352                                   704
 32                       480                                   960

1 SELECT2 scheduler_address,3 scheduler_id,4 cpu_id,5 status,6 current_tasks_count,7 current_workers_count,active_workers_count8 FROM sys.dm_os_schedulers

 如果大家有什麼需要補充的，或者文章有不正確的，歡迎大家拍磚！！

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 2013-6-15 做了一下補充，如果SQLSERVER存在要等待的資源，那麼執行下面語句就會顯示出會話中有多少個worker在等待

結合[sys].[dm_os_wait_stats]視圖，如果當前SQLSERVER裡面沒有任何等待資源，那麼下面的SQL語句不會顯示任何結果

 1 SELECT TOP 10 2  [session_id], 3  [request_id], 4  [start_time] AS ‘開始時間‘, 5  [status] AS ‘狀態‘, 6  [command] AS ‘命令‘, 7  dest.[text] AS ‘sql語句‘,  8  DB_NAME([database_id]) AS ‘資料庫名‘, 9  [blocking_session_id] AS ‘正在阻塞其他會話的會話ID‘,10  der.[wait_type] AS ‘等待資源類型‘,11  [wait_time] AS ‘等待時間‘,12  [wait_resource] AS ‘等待的資源‘,13  [dows].[waiting_tasks_count] AS ‘當前進行中等待的任務數‘,14  [reads] AS ‘物理讀次數‘,15  [writes] AS ‘寫次數‘,16  [logical_reads] AS ‘邏輯讀次數‘,17  [row_count] AS ‘返回結果行數‘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

 比如我當前執行了查詢SalesOrderDetail_test表100次，由於表資料非常多，所以SSMS需要把SQLSERVER執行的結果慢慢的取走，

造成了ASYNC_NETWORK_IO等待

1 USE [AdventureWorks]2 GO3 SELECT * FROM dbo.[SalesOrderDetail_test]4 GO 100

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經過排查和這幾天的觀察情況，確定是某些表缺失索引導致，現在在這些表上增加了索引，問題解決了

1 select * from t_AccessControl        --許可權控製表許可權控制2 select * from t_GroupAccess            --使用者組許可權表使用者組許可權3 select * from t_GroupAccessType        --使用者組權限類別表使用者組權限類別4 select * from t_ObjectAccess        --對象許可權表對象許可權5 select * from t_ObjectAccessType    --對象權限類別型表對象權限類別型6 select * from t_ObjectType            --物件類型表物件類型

查詢CPU佔用高的語句

 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_text10 FROM sys.dm_exec_query_stats11 ORDER BY [avg_cpu_cost] DESC

查詢缺失索引

1 SELECT 2     DatabaseName = DB_NAME(database_id)3     ,[Number Indexes Missing] = count(*) 4 FROM sys.dm_db_missing_index_details5 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_handle13 ORDER BY [Total Cost] DESC;

定位問題後，建立非叢集索引

1 CREATE NONCLUSTERED INDEX IX_t_AccessControl_F4 ON dbo.t_AccessControl2 (3     FObjectType4 )include([FUserID], [FAccessType], [FAccessMask]) WITH( STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]5 GO6 7 drop index IX_t_AccessControl_F4 on t_AccessControl

 CPU佔用恢複正常

SQLSERVER排查CPU佔用高的情況