[SERVER-29465] Add warning about Windows SystemFileCacheSize for WiredTiger Created: 06/Jun/17  Updated: 30/Oct/23  Resolved: 10/Nov/17

Status: Closed
Project: Core Server
Component/s: Internal Code
Affects Version/s: None
Fix Version/s: 3.6.0-rc4

Type: Improvement Priority: Major - P3
Reporter: Alexander Gorrod Assignee: Xiangyu Yao (Inactive)
Resolution: Fixed Votes: 0
Labels: neweng
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Depends
depends on DOCS-10929 Warning about Windows SystemFileCache... Closed
is depended on by SERVER-33706 Remove warning message about Windows ... Closed
Documented
is documented by DOCS-10929 Warning about Windows SystemFileCache... Closed
Related
is related to SERVER-20991 WiredTiger caching strategy needs imp... Closed
Backwards Compatibility: Fully Compatible
Sprint: Storage 2017-10-23, Storage 2017-11-13
Participants:
Case:

 Description   

Some MongoDB users on Windows have switched to enabling direct_io because the file system cache on Windows is greedy by default and can lead to content in allocated memory getting swapped out - which leads to terrible performance.

Windows provides the SetSystemFileCacheSize API that allows limiting the amount of memory that can be used by the file system cache. The setting is global across the computer.

We could add code into MongoDB that calls the API, and limits the amount of memory the file system cache can use to a percentage of available memory.

The call should only be done for storage engines that have a cache management layer. MMAP relies on the file system cache using all available memory - limiting how much memory is available would hurt MMAP users.

There is further discussion in SERVER-20991.



 Comments   
Comment by Muhammad Yahya (Inactive) [ 17/Feb/20 ]

Upgrading to newer version of 3.6 will get rid of this issue?

Comment by Githook User [ 10/Nov/17 ]

Author:

{'name': 'Xiangyu Yao', 'username': 'xy24', 'email': 'xiangyu.yao@mongodb.com'}

Message: SERVER-29465 Add warning about Windows SystemFileCacheSize for WiredTiger
Branch: master
https://github.com/mongodb/mongo/commit/eaf6c96f4893946cd62d6565d3aab92901b92ad8

Comment by Xiangyu Yao (Inactive) [ 18/Oct/17 ]

After talking to Alex via Slack, I decided to use 40% as the percentage threshold (SystemFileCacheSize/TotalMemory) for this warning. - it matches in well with the default WiredTiger cache size, which is around 50%.

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