(Republishing, or using this info in a commercial product/website, is prohibited without permission. All other uses are permitted. If in doubt, please ask.)
This wait type is when a free list stall occurs in the buffer pool. This means that a new page needs to be created but there isn’t any free memory in the buffer pool, so the thread sleeps for a very short period of time (in SQL Server 2005 in was 10ms), assuming that while it is asleep something (e.g. the lazywriter) will free up some memory. When this wait occurs, you will see a blip in the Buffer Manager:Free list stalls/sec perfmon counter.
(Books Online description: N/A)
Questions/comments on this wait type? Click here to send Paul an email, especially if you have any information to add to this topic.
Added in SQL Server version:
Removed in SQL Server version:
Extended Events wait_type value:
The map_key value in sys.dm_xe_map_values is 1396 in 2019 CU12. After 2019 CU12, you must check the DMV to get the latest value as some map_key values have changed in later builds.
I have not seen this wait type be a noticeable contention point, but if they start to increase on your system, that’s a sign that the buffer pool is under memory pressure, which may indicate other problems on the instance.
Known occurrences in SQL Server (list number matches call stack list):
- Free list stall (in this case, as part of allocating a page for the version store in tempdb)
- Free list stall (in this case, as part of performing readahead during an index scan)
And other similar call stacks.
Abbreviated call stacks (list number matches known occurrences list):