Sql-server – RAM utilization

The formulas that tuning scripts like mysqltuner use to estimate potential memory usage are bunk. These posts explain why and give some examples of things that could be causing the memory usage pattern you're seeing:

How much memory can MySQL use in the worst case?

MySQL Server Memory Usage

This post talks about isolating the problem by running tests:

Troubleshooting MySQL Memory Usage

The simplest explanation is that there is a query with large memory overhead, which should be identifiable by running the query in isolation and observing its impact on memory usage.

As the post says, memory usage issues are one of the more annoying problems to have in MySQL, and the lack of instrumentation features that other RDBMS have really shows here and makes this type of problem difficult to diagnose.

SQL Server is using the AWE memory allocation API to allocate buffer pool memory if "lock pages in memory" is enabled.

If SQL Server's max server memory setting is not set, SQL Server will eventually use as much memory as it needs. That will largely show up as AWE memory in RAMMap. A little more detail can be found here and all the SQL Server memory settings are explained here.

You should set the max server memory setting to allow an adequate amount for the operating system. If not enough memory is available for the OS, paging can occur and cause performance issues. A good starting point is 3 to 4 GB reserved for the OS, but watch the appropriate counters to see if the OS is under memory pressure.

You can get more information about how to select the right max server memory setting at the following links:

• A Sysadmin’s Guide to Microsoft SQL Server Memory by Brent Ozar
• Importance of setting Max Server Memory in SQL Server and How to Set it by Sakthivel Chidambaram

Full details of how SQL Server uses AWE and Locked Pages can be found in the Microsoft CSS SQL Server Engineers article:

Fun with Locked Pages, AWE, Task Manager, and the Working Set