I would focus on core points
When we check high physical memory usage in the task manager it shows nearly 90 to 95 % full but I have checked all system processes which are taking nearly 2-3GB RAM memory.
You are doing mistake, which probably many newbies do when referring to memory utilized by SQL Server. SQL Server would never show you correct memory utilization in task manager if Locked pages in memory privilege(LPIM) is there for account running SQL Server service because task manager only shows
Process Private Bytes, the memory allocated via Virtual_alloc function which is pageable. Now if SQL server service account has LPIM most part of memory allocation would be done by AWE API and this allocated memory is NON pageable and thus does not comes under task manager,in the end showing you different values. Hope this is clear
Other point to note is task manager shows memory utilized by all OS processes so why are you even referring to it and making wrong conclusion about SQL Server. Remember Task manager is Windows tool not a SQL Server tool.
I used the RAMmap tool to check the running processes' memory and it is showing AWE process which is using this extra memory. AWE is not releasing this memory but when we increase the RAM then it is capturing all the free RAM memory slowly.
RAMMAP is not the tool of your interest again. If you want to check memory utilized by SQL Server 2008 and above you can use below query.
select (physical_memory_in_use_kb/1024) as Phy_Mem_in_MB,
(locked_page_allocations_kb/1024) as Mem_allocated_AWE_MB,
(virtual_address_space_committed_kb/1024) as Total_memory_utilized
Can you please add the output of above query in question and lets see how much memory AWE API is allocating.
Does anyone know how to reduce this AWE memory usage?
As already noted AWE is an Windows API
not SQL Server functionality, which does memory allocation for SQL Server process if account running SQL Server has LPIM. You can use
to clear memory allocated via AWE API but I would not advise you to run that specially on production server. Its pretty much normal for SQL Server to use memory, and good thing is when there is memory crunch SQL Server would even trim down its memory consumption upto Min server memory value and release memory.