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How do i check memory usage by my SQL server in production box. I am using SQL Server 2016.When ever i check task manager,it shows above 90%. I don't think that is the real memory usage by sql server.

I have a SQL performance tool grafana which shows CPU usage very less than what i see in task manager. I checked Resource Monitor,there is can see Average CPU value.I am confused as to which is the SQL server memory usage. I am trying to determine if memory pressure is an issue to some of my problem.

Can someone direct to a good/proper explanation.

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4 Answers 4

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Can someone direct to a good/proper explanation.

I would start by saying Task Manager is not a correct place to gauge SQL Server memory consumption, it will not tell you correct value when SQL Server service account has Locked Pages in Memory(LPIM) privilege. This is because normally task manager tracks Process Private bytes which is pageable memory and allocated via VirtualAlloc() function but with Service account having LPIM chunk of memory allocation is done by AWE API which is NON pageable so task manager does not tracks it and this can lead to incorrect value.

It is quite normal for SQL Server to utilize memory allocated to it which often seems like it is using high memory but this is quite normal. Don`t panic if some tool is showing low CPU utilization and task manager is showing high memory this may be just normal. To know how much physical memory SQL Server is using please use below query

select
(physical_memory_in_use_kb/1024)Phy_Memory_usedby_Sqlserver_MB,
(locked_page_allocations_kb/1024 )Locked_pages_used_Sqlserver_MB,
(virtual_address_space_committed_kb/1024 )Total_Memory_UsedBySQLServer_MB,
process_physical_memory_low,
process_virtual_memory_low
from sys. dm_os_process_memory

Phy_Memory_usedby_Sqlserver_MB-- Gives total Physical memory used by SQL Server in MB Total_Memory_usedBy_SQLServer_MB-- Gives total memory(RAM+Page file) used by SQL Server in MB

To read more about why task manager should not be used see Fun with Locked Pages, AWE, Task Manager, and the Working Set…

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22

'I am trying to determine if memory pressure is an issue to some of my problem.'

very useful script: https://github.com/ktaranov/sqlserver-kit/blob/master/Scripts/SQLServer_Memory_Information.sql

you see verbose memory utilization: enter image description here

https://www.sqlskills.com/blogs/glenn/sql-server-diagnostic-information-queries-for-november-2017/ SQL Server 2017 Diagnostic Information Queries:
see comment 

-- Page Life Expectancy (PLE) value for each NUMA node in current instance  (Query 46) (PLE by NUMA Node)
SELECT @@SERVERNAME AS [Server Name], RTRIM([object_name]) AS [Object Name], instance_name, cntr_value AS [Page Life Expectancy]
FROM sys.dm_os_performance_counters WITH (NOLOCK)
WHERE [object_name] LIKE N'%Buffer Node%' -- Handles named instances
AND counter_name = N'Page life expectancy' OPTION (RECOMPILE);
------

-- PLE is a good measurement of internal memory pressure
-- Higher PLE is better. Watch the trend over time, not the absolute value

(Query 14) 

-- Good basic information about OS memory amounts and state  (Query 14) (System Memory)
SELECT total_physical_memory_kb/1024 AS [Physical Memory (MB)], 
       available_physical_memory_kb/1024 AS [Available Memory (MB)], 
       total_page_file_kb/1024 AS [Total Page File (MB)], 
       available_page_file_kb/1024 AS [Available Page File (MB)], 
       system_cache_kb/1024 AS [System Cache (MB)],
       system_memory_state_desc AS [System Memory State]
FROM sys.dm_os_sys_memory WITH (NOLOCK) OPTION (RECOMPILE);
------

-- You want to see "Available physical memory is high" for System Memory State
-- This indicates that you are not under external memory pressure

-- Possible System Memory State values:
-- Available physical memory is high
-- Physical memory usage is steady
-- Available physical memory is low
-- Available physical memory is running low
-- Physical memory state is transitioning

(47) 

-- Memory Grants Pending value for current instance  (Query 47) (Memory Grants Pending)
SELECT @@SERVERNAME AS [Server Name], RTRIM([object_name]) AS [Object Name], cntr_value AS [Memory Grants Pending]
FROM sys.dm_os_performance_counters WITH (NOLOCK)
WHERE [object_name] LIKE N'%Memory Manager%' -- Handles named instances
AND counter_name = N'Memory Grants Pending' OPTION (RECOMPILE);
------

-- Run multiple times, and run periodically if you suspect you are under memory pressure
-- Memory Grants Pending above zero for a sustained period is a very strong indicator of internal memory pressure

(62) 

-- Top Cached SPs By Total Logical Reads. Logical reads relate to memory pressure  (Query 62) (SP Logical Reads)
SELECT TOP(25) p.name AS [SP Name], qs.total_logical_reads AS [TotalLogicalReads], 
qs.total_logical_reads/qs.execution_count AS [AvgLogicalReads],qs.execution_count, 
ISNULL(qs.execution_count/DATEDIFF(Minute, qs.cached_time, GETDATE()), 0) AS [Calls/Minute], 
qs.total_elapsed_time, qs.total_elapsed_time/qs.execution_count AS [avg_elapsed_time],
CASE WHEN CONVERT(nvarchar(max), qp.query_plan) LIKE N'%<MissingIndexes>%' THEN 1 ELSE 0 END AS [Has Missing Index], 
FORMAT(qs.last_execution_time, 'yyyy-MM-dd HH:mm:ss', 'en-US') AS [Last Execution Time], 
FORMAT(qs.cached_time, 'yyyy-MM-dd HH:mm:ss', 'en-US') AS [Plan Cached Time]
-- ,qp.query_plan AS [Query Plan] -- Uncomment if you want the Query Plan
FROM sys.procedures AS p WITH (NOLOCK)
INNER JOIN sys.dm_exec_procedure_stats AS qs WITH (NOLOCK)
ON p.[object_id] = qs.[object_id]
CROSS APPLY sys.dm_exec_query_plan(qs.plan_handle) AS qp
WHERE qs.database_id = DB_ID()
AND DATEDIFF(Minute, qs.cached_time, GETDATE()) > 0
ORDER BY qs.total_logical_reads DESC OPTION (RECOMPILE);
------

-- This helps you find the most expensive cached stored procedures from a memory perspective
-- You should look at this if you see signs of memory pressure

(63) 

-- Top Cached SPs By Total Physical Reads. Physical reads relate to disk read I/O pressure  (Query 63) (SP Physical Reads)
SELECT TOP(25) p.name AS [SP Name],qs.total_physical_reads AS [TotalPhysicalReads], 
qs.total_physical_reads/qs.execution_count AS [AvgPhysicalReads], qs.execution_count, 
qs.total_logical_reads,qs.total_elapsed_time, qs.total_elapsed_time/qs.execution_count AS [avg_elapsed_time],
CASE WHEN CONVERT(nvarchar(max), qp.query_plan) LIKE N'%<MissingIndexes>%' THEN 1 ELSE 0 END AS [Has Missing Index],
FORMAT(qs.last_execution_time, 'yyyy-MM-dd HH:mm:ss', 'en-US') AS [Last Execution Time], 
FORMAT(qs.cached_time, 'yyyy-MM-dd HH:mm:ss', 'en-US') AS [Plan Cached Time]
-- ,qp.query_plan AS [Query Plan] -- Uncomment if you want the Query Plan 
FROM sys.procedures AS p WITH (NOLOCK)
INNER JOIN sys.dm_exec_procedure_stats AS qs WITH (NOLOCK)
ON p.[object_id] = qs.[object_id]
CROSS APPLY sys.dm_exec_query_plan(qs.plan_handle) AS qp
WHERE qs.database_id = DB_ID()
AND qs.total_physical_reads > 0
ORDER BY qs.total_physical_reads DESC, qs.total_logical_reads DESC OPTION (RECOMPILE);
------

-- This helps you find the most expensive cached stored procedures from a read I/O perspective
-- You should look at this if you see signs of I/O pressure or of memory pressure

(64) 

-- Top Cached SPs By Total Logical Writes (Query 64) (SP Logical Writes)
-- Logical writes relate to both memory and disk I/O pressure 
SELECT TOP(25) p.name AS [SP Name], qs.total_logical_writes AS [TotalLogicalWrites], 
qs.total_logical_writes/qs.execution_count AS [AvgLogicalWrites], qs.execution_count,
ISNULL(qs.execution_count/DATEDIFF(Minute, qs.cached_time, GETDATE()), 0) AS [Calls/Minute],
qs.total_elapsed_time, qs.total_elapsed_time/qs.execution_count AS [avg_elapsed_time],
CASE WHEN CONVERT(nvarchar(max), qp.query_plan) LIKE N'%<MissingIndexes>%' THEN 1 ELSE 0 END AS [Has Missing Index], 
FORMAT(qs.last_execution_time, 'yyyy-MM-dd HH:mm:ss', 'en-US') AS [Last Execution Time], 
FORMAT(qs.cached_time, 'yyyy-MM-dd HH:mm:ss', 'en-US') AS [Plan Cached Time]
-- ,qp.query_plan AS [Query Plan] -- Uncomment if you want the Query Plan 
FROM sys.procedures AS p WITH (NOLOCK)
INNER JOIN sys.dm_exec_procedure_stats AS qs WITH (NOLOCK)
ON p.[object_id] = qs.[object_id]
CROSS APPLY sys.dm_exec_query_plan(qs.plan_handle) AS qp
WHERE qs.database_id = DB_ID()
AND qs.total_logical_writes > 0
AND DATEDIFF(Minute, qs.cached_time, GETDATE()) > 0
ORDER BY qs.total_logical_writes DESC OPTION (RECOMPILE);
------

-- This helps you find the most expensive cached stored procedures from a write I/O perspective
-- You should look at this if you see signs of I/O pressure or of memory pressure

P.S. this is not an exhaustive answer

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I am not sure about the tool grafana, but if you run the query below it shows the currently allocated memory

SELECT  
(physical_memory_in_use_kb/1024) AS Memory_usedby_Sqlserver_MB,  
(locked_page_allocations_kb/1024) AS Locked_pages_used_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;
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You should leave out task manager as it does not properly report memory allocation information in some cases, depending on memory allocation routines application uses. From OS, you should be good with perfmon, as it should report memory usage properly. You can also use SQL DMVs reporting memory information, e.g. sys.dm_os_sys_memory (there are more memory related dmvs depending on your needs and SQL Server version).

Here is an article explaining task manager inaccurately reporting SQL Server memroy usage:

LINK: stop-using-task-manager-to-check-sqls-memory-usage

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