sql server high cpu 排查

refer: 

https://techcommunity.microsoft.com/t5/azure-sql/monitor-cpu-usage-on-sql-server-and-azure-sql/ba-p/680777

https://www.cnblogs.com/lyhabc/archive/2013/06/12/3133273.html (step by step)

https://www.360kuai.com/mob/transcoding?url=9d1f5d2101d40ebc7&cota=4&kuai_so=1&sign=360_e39369d1

https://stackoverflow.com/questions/1289558/how-much-ram-is-sql-server-actually-using

https://stackoverflow.com/questions/7197574/script-to-kill-all-connections-to-a-database-more-than-restricted-user-rollback

https://stackoverflow.com/questions/941763/list-the-queries-running-on-sql-server

通常 CPU high 和缺 ram 有密切关系. 

start > administrative tools > performance > open resource monitor > 这里看到 ram 和 cpu 的 detail 

OS ram 多, 不代表 sql 可以用得多. 要去 server > properties > memory 看 max ram 是多少. 

常用语句

0. 查 cpu, connection 

<=50 都是 sa background job (最好也看一下)

USE master
GO
SELECT * FROM sys.[sysprocesses] WHERE [spid] > 50 --AND DB_NAME([dbid])='gposdb'
SELECT COUNT(*) FROM [sys].[dm_exec_sessions] WHERE [session_id]>50

1. 查 connections

SELECT
DB_NAME(DBID) AS DataBaseName
,COUNT(DBID) AS NumberOfConnections
,LogiName
FROM sys.sysprocesses
WHERE DBID > 0
GROUP BY DBID, LogiName

2. sum connect count 

select SUM(NumberOfConnections) from (
SELECT 
    DB_NAME(DBID) AS DataBaseName
    ,COUNT(DBID) AS NumberOfConnections
    ,LogiName 
FROM sys.sysprocesses
WHERE DBID > 0
GROUP BY DBID, LogiName
) a

3. 查 ram usage

SELECT
(total_physical_memory_kb/1024) AS Total_OS_Memory_MB,
(available_physical_memory_kb/1024)  AS Available_OS_Memory_MB,
ROUND(100 - CAST(((available_physical_memory_kb/1024) * 100.0/ (total_physical_memory_kb/1024)) AS FLOAT),2) AS Usage_Percentage
FROM sys.dm_os_sys_memory;

SELECT  
(physical_memory_in_use_kb/1024) AS Memory_used_by_Sqlserver_MB,  
(locked_page_allocations_kb/1024) AS Locked_pages_used_by_Sqlserver_MB,  
(total_virtual_address_space_kb/1024) AS Total_VAS_in_MB,
process_physical_memory_low,  
process_virtual_memory_low  
FROM sys.dm_os_process_memory;