[SERVER-38815] Expose an absolute dirty size to the eviction configuration parameters Created: 03/Jan/19 Updated: 29/Oct/23 Resolved: 08/Sep/21 |
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| Status: | Closed |
| Project: | Core Server |
| Component/s: | WiredTiger |
| Affects Version/s: | None |
| Fix Version/s: | 5.1.0-rc0 |
| Type: | New Feature | Priority: | Major - P3 |
| Reporter: | Dmitry Agranat | Assignee: | Josef Ahmad |
| Resolution: | Fixed | Votes: | 3 |
| Labels: | louis-preferred | ||
| Remaining Estimate: | Not Specified | ||
| Time Spent: | Not Specified | ||
| Original Estimate: | Not Specified | ||
| Issue Links: |
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| Backwards Compatibility: | Fully Compatible | ||||||||||||||||||||||||
| Backport Requested: |
v4.4, v4.2, v4.0, v3.6
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| Sprint: | Storage Engines 2019-01-28, Execution Team 2020-05-04, Execution Team 2020-05-18, Execution Team 2020-06-01, Execution Team 2021-09-06, Execution Team 2021-09-20 | ||||||||||||||||||||||||
| Participants: | |||||||||||||||||||||||||
| Case: | (copied to CRM) | ||||||||||||||||||||||||
| Description |
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Expose two configurable options that control the targeted and maximum levels of dirty data allowed in cache. The options will accept a floating-point value in gigabytes, like cacheSizeGB. eviction_dirty_target can be thought of as the targeted amount of dirty data allowed in cache. Anything larger, and worker threads start eviction. |
| Comments |
| Comment by Githook User [ 08/Sep/21 ] |
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Author: {'name': 'Josef Ahmad', 'email': 'josef.ahmad@mongodb.com', 'username': 'josefahmad'}Message: |
| Comment by Geert Bosch [ 24/Jun/21 ] |
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I don't understand: a customer should be able to know the memory size of their server and configure an appropriate percentage. It would seem that expressing the value as an absolute number is just a shortcut to doing the computation for a specific configuration. I can see how it might make sense to use absolute values in some circumstances, but I fail to understand how it's more than a convenience. On a related note, it doesn't seem unreasonable to assume that checkpointing resource (in terms of IOPS and avalable compute power) scales to some degree with the memory size, so a 1 TB system should be OK writing 1 GB/sec while a 16GB system would be maxed out at 50 MB/sec. dmitry.agranat, could you give some clarification whether an absolute size is a convenience feature or more than that? |
| Comment by Dianna Hohensee (Inactive) [ 27/May/20 ] |
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So WT's solution in We do not pass eviction settings through MongoDB today. We won't change that. I will add a new MongoDB server parameter just for absolute dirty cache size. |