no free memory but low total memory

Question

I have SQL Server 2012 SP2 that has a max memory of 25.4GB but SQL Server is only using 15GB. When I check free memory with the PerfMon SQLServer:Memory Manger Free Memory (KB) counter only 40MB is free. The server itself has 32GB.

I think that the server is only using 15GB because it only needs that much for loading all the used pages. But what I do not understand is why the free memory is only 40MB.

Can someone please explain this?

There are no other services on the system and my PLE is 122000 seconds.

Answer 1

The counter Memory Manager: Free Memory (KB) tells you below. Read the BOL document

Free Memory (KB): Specifies the amount of committed memory currently not used by the server.

So what this means is of all committed memory SQL Server is not using 40 MB of the memory. This is not telling you free memory on the SQL Server system. A committed memory is one that is backed by physical RAM. When a process starts it can address any physical memory address in its VAS but memory will only be committed if that VAS region is backed by physical memory.