[SERVER-23321] Allow pinning specific WT collections in memory Created: 23/Mar/16  Updated: 06/Dec/22  Resolved: 11/May/20

Status: Closed
Project: Core Server
Component/s: Storage, WiredTiger
Affects Version/s: None
Fix Version/s: None

Type: New Feature Priority: Major - P3
Reporter: Bruce Lucas (Inactive) Assignee: Backlog - Storage Execution Team
Resolution: Won't Do Votes: 5
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Related
is related to WT-2452 Implement a mechanism that gives prio... Closed
Assigned Teams:
Storage Execution
Participants:
Case:

 Description   

There are use cases that would benefit from the ability to keep an infrequently used collection in cache to reduce latency of queries to that collection.



 Comments   
Comment by Eric Milkie [ 11/May/20 ]

Rather than adding the proposed knob, the recommended way of reducing paging is to adjust workloads or add cache memory. Certainly if a collection is read frequently, the eviction algorithm is already deprioritizing such pages when considering them for eviction. If the pages are still being evicted, the system must need that cache memory for other immediate purposes and preventing this eviction will lead to other problems.

Pinning certain tables into memory such that the pages cannot be evicted can introduce new cache-full and eviction failure scenarios, so I am closing this as Won't-Do.

Comment by Hrushikesh [X] [ 28/Aug/18 ]

We have a collection that goes through heavy read operation quite frequently. Due to other collections in the Mongo cluster being too large, the pages are getting evicted and read operations are reaching disk. This is a typical identities types collection which are accessed quite often by various modules in our product. 

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