[SERVER-27927] Maximum thread cache byte limit should change based on number of connections Created: 06/Feb/17 Updated: 27/Oct/23 Resolved: 18/Dec/17 |
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| Status: | Closed |
| Project: | Core Server |
| Component/s: | None |
| Affects Version/s: | 3.4.2, 3.5.2 |
| Fix Version/s: | None |
| Type: | Improvement | Priority: | Major - P3 |
| Reporter: | Andrew Young | Assignee: | Mark Benvenuto |
| Resolution: | Works as Designed | Votes: | 0 |
| Labels: | tcmalloc | ||
| Remaining Estimate: | Not Specified | ||
| Time Spent: | Not Specified | ||
| Original Estimate: | Not Specified | ||
| Backwards Compatibility: | Fully Compatible |
| Sprint: | Platforms 2018-01-01 |
| Participants: | |
| Case: | (copied to CRM) |
| Description |
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Currently, a mongos instance will attempt to cleanup memory from a thread's cache during threadStateChange() if the thread's cache size is larger than 10,000 bytes. This number was chosen heuristically based on having no more than 1,000 clients connected to a mongos instance. If there are more than 1,000 clients, then the cleanup code is run far more often. This is also problematic as the mongos logs a debug message every time the cleanup is performed. The suggested improvement is to adjust the maximum thread cache size value based on the number of currently active client connections. The code that this change relates to is located in https://github.com/mongodb/mongo/blob/r3.4.2/src/mongo/util/tcmalloc_server_status_section.cpp#L68-L86 |
| Comments |
| Comment by Mark Benvenuto [ 18/Dec/17 ] |
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TCMalloc already dynamically adjusts the individual thread sizes, and ensures a minimum of 512KB per thread. There are not plans to adjust the thread cache based on the number of threads in MongoDB. In 3.6, we have disabled markThreadIdle by default so the messages will not be logged. |
| Comment by Eric Milkie [ 06/Feb/17 ] |
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We should also consider calling BecomeTemporarilyIdle(), which was added recently to TCMalloc and is intended to do what we need here, rather than calling MarkThreadIdle() and MarkThreadBusy(). |