here were various changes to memory related DMVs, DBCC memory status, and Perfmon counters in SQL Server 2012 as part of the redesign of the Memory Manager component of SQLOS. The Memory Manager redesign resulted in being able to more accurately size and govern all SQL Server memory consumption, making page allocations more efficient, and better handling and tracking of NUMA node memory allocations. This post aims to document these surface area changes in one place to serve as a quick reference.
Some of these changes were to standardize memory counters as “kb” rather than bytes or pages, continuing a process begun earlier, but now more relevant since the single and multi-page allocators were replaced by an any-size page allocator, so counting pages allocated would no longer give a meaningful view of memory use. This consolidation of allocators also resulted consolidated counters for page allocation.
Other changes reflect the central role of the redesigned Memory Manager in being the interface to the OS, providing page allocations for the other components. A modular summary of the architectural changes is shown below:
DMV Changes
sys.dm_os_memory_nodes
The consolidation of the single and multi-page allocators is reflected in the pages_kb column in sys.dm_os_memory_nodes. The new foreign_committed_kb counter is a result of the improved NUMA management and reporting in SQL 2012 and identifies memory on a noe that belongs to a remote node, which can be useful if you’re troubleshooting slower memory access. We will always try and use local memory first, at least until the target memory is reached.
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sys.dm_os_memory_nodes |
|
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SQL Server 2012 |
SQL Server 2008 R2 |
|
pages_kb |
single_pages_kb + |
|
foreign_committed_kb |
– |
sys.dm_os_sys_info
The main memory manager changes here are to standardize memory counters.
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sys.dm_os_sys_info |
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SQL Server 2012 |
SQL Server 2008 R2 |
|
physical_memory_kb |
physical_memory_in_bytes |
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virtual_memory_kb |
virtual_memory_in_bytes |
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committed_kb |
bpool_committed |
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committed_target_kb |
bpool_commit_target |
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visible_target_kb |
bpool_visible |
sys.dm_os_memory_cache_counters
|
sys.dm_os_memory_cache_counters |
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|
SQL Server 2012 |
SQL Server 2008 R2 |
|
pages_kb |
single_pages_kb + |
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pages_in_use_kb |
single_pages_in_use_kb |
sys.dm_os_memory_cache_entries
|
sys.dm_os_memory_cache_entries |
|
|
SQL Server 2012 |
SQL Server 2008 R2 |
|
pages_kb |
pages_allocated_count |
sys.dm_os_memory_clerks
|
sys.dm_os_memory_clerks |
|
|
SQL Server 2012 |
SQL Server 2008 R2 |
|
pages_kb |
single_pages_kb + |
|
page_size_in_bytes |
page_size_bytes |
sys.dm_os_memory_objects
|
sys.dm_os_memory_objects |
|
|
SQL Server 2012 |
SQL Server 2008 R2 |
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pages_in_bytes |
pages_allocated_count |
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max_pages_in_bytes |
max_pages_allocated_count |
DBCC Memory Status changes
Many of the DBCC memory counters that were previously under Buffer Pool have now been consolidated under Memory Manager to reflect the revised architecture. There is also some additional information to reflect OS errors and NUMA awareness. NUMA growth phase shows memory growth before the target is reached. The “Pages In Use” counter shows the actual number of pages in use, including the stolen pages, database pages, and the reserved memory. The Away Committed counter indicates how much memory from this node is committed from other nodes.
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SQL Server |
SQL Server |
|
Memory Manager |
– |
|
Memory Manager |
Memory Manager |
|
Memory Manager Emergency |
Memory Manager |
|
Memory Manager |
Buffer Pool |
|
Memory Manager |
Buffer Pool |
|
Memory Manager |
Buffer Pool |
|
Memory Manager |
Buffer Pool |
|
Memory Manager |
Buffer Pool Free |
|
Memory Manager |
– |
|
Memory Manager |
Buffer Pool |
|
Memory Manager |
– |
|
Memory Manager |
Buffer Pool Last |
|
Memory Manager |
– |
|
SQL Server |
SQL Server |
|
Memory Manager |
– |
|
Memory Manager |
Memory Manager |
|
Memory Manager |
Memory Manager |
|
Memory Manager |
Buffer Pool |
|
Memory Manager Current |
Buffer Pool |
|
Memory Manager |
Buffer Pool |
|
Memory Manager |
Buffer Pool |
|
Memory Manager |
Buffer Pool Free |
|
Memory Manager |
– |
|
Memory Manager |
Buffer Pool |
|
Memory Manager |
– |
|
Memory Manager |
Buffer Pool Last |
|
Memory Manager |
– |
|
SQL Server |
SQL Server |
|
Memory node Id = n |
Memory node Id = n |
|
Memory node Id = n |
– |
|
Memory node Id = n |
– |
|
Memory node Id = n |
– |
|
Memory node Id = n |
– |
|
Memory Clerks |
Memory Clerks |
Perfmon counters
The Perfmon counter changes follow the same consolidation of counters under the Memory Manager object, and the standardization of counters to KB. Several deprecated AWE counters are now removed.
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SQL Server 2012 |
SQL Server 2008 R2 |
|
Object – SQLServer:Memory |
Object – SQLServer:Buffer |
|
Database Cache Memory (KB) |
Database pages |
|
Free Memory (KB) |
Free pages |
|
Reserved Server Memory (KB) |
Reserved pages |
|
Stolen Server Memory (KB) |
Stolen pages |
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Target |
Target |
|
Total |
Total |
|
– |
AWE |
|
– |
AWE stolen maps / sec |
|
– |
AWE |
|
– |
AWE |
|
– |
AWE |
|
SQL Server |
SQL Server |
|
Object – |
Object – |
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Database Node |
Database pages |
|
Free Node Memory |
Free pages |
|
Foreign Node Memory |
Foreign pages |
|
Stolen Node Memory |
Stolen pages |
|
Target Node Memory |
Target pages |
|
Total Node Memory |
Total pages |
I’ll follow up this article with some additional surface area changes for configuration and new memory manager messages that appear in the errorlog.
The goal of these changes is to make the new Memory Manager activity easier and more intuitive to track, and to clean up some of the values that no longer make sense with the any size page allocator and deprecation of AWE. Anything you used to use but can’t find any more? Let me know.