[SERVER-24267] MongoDB is not utilizing all available memory. Created: 24/May/16  Updated: 26/May/16  Resolved: 24/May/16

Status: Closed
Project: Core Server
Component/s: Performance
Affects Version/s: 3.2.0
Fix Version/s: None

Type: Question Priority: Major - P3
Reporter: Yang Assignee: Unassigned
Resolution: Done Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Participants:

 Description   

I have a stand-alone MongoDB instance running in windows. It's recently experiencing slowness and my troubleshooting has found the following symptoms:

1. The slowness normally occurs after a full text search query against a huge collection. I guess this is because it swaps many pages in the collection from disk into memory hence data from other collections are squeezed out of memory.

2. The server memory usage is capped around 55%. The server (Win2012) has 32GB of memory but MongoDB is not trying to utilize beyond 16GB.

I have seen a couple of Q&A in limiting MongoDB memory usage but not on how to encourage MongoDB to be more greedy.

MongoDB: 3.2.0
Storage Engine: wiredTiger
OS: Win2012
Memory: 32GB



 Comments   
Comment by Yang [ 26/May/16 ]

Hi Dan, thanks a lot. This is indeed the cause.

Comment by Daniel Pasette (Inactive) [ 25/May/16 ]

Hi xuguoming@nexlabs.com, this link in the documentation may help understand the relationship between the WiredTiger cache size and file system cache. https://docs.mongodb.com/manual/faq/storage/#to-what-size-should-i-set-the-wiredtiger-cache

Comment by Ramon Fernandez Marina [ 24/May/16 ]

xuguoming@nexlabs.com, please note that the SERVER project is for reporting bugs or feature suggestions for the MongoDB server. For MongoDB-related support discussion please post on the mongodb-user group or Stack Overflow with the mongodb tag, where your questions will reach a larger audience. Questions like these involving more discussion would be best posted on the mongodb-user group. See also our Technical Support page for additional support resources.

Regards,
Ramón.

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