[SERVER-27792] mongod is swapping with free ram and vm.swappinnes = 0 Created: 23/Jan/17 Updated: 24/Jan/17 Resolved: 24/Jan/17 |
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| Status: | Closed |
| Project: | Core Server |
| Component/s: | WiredTiger |
| Affects Version/s: | 3.2.5 |
| Fix Version/s: | None |
| Type: | Question | Priority: | Major - P3 |
| Reporter: | Igor Chelnokov [X] | Assignee: | Ramon Fernandez Marina |
| Resolution: | Done | Votes: | 0 |
| Labels: | None | ||
| Remaining Estimate: | Not Specified | ||
| Time Spent: | Not Specified | ||
| Original Estimate: | Not Specified | ||
| Participants: |
| Description |
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Hello We're running MongoDB 3.2.5 in a Docker container (official image). System info: vm.zone_reclaim_mode = 0 I assume that mongod is run with numactl --interleave=all Engine used is wiredTiger. System RAM stats as per free -m: Also, we have another instance of MongoDB on this same machine - 2.6, although it's barely ever used, it uses swap too (~5M with 41M RSS). So, why does mongod use swap with free RAM available and vm.swappiness = 0? |
| Comments |
| Comment by Igor Chelnokov [X] [ 24/Jan/17 ] |
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Thanks for your answer! |
| Comment by Ramon Fernandez Marina [ 24/Jan/17 ] |
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Gendalph, the decision on when to use or not use swap is made by the OS, not by any user process. Wikipedia has a simple explanation of what vm.swappiness does, and a pointer to the Linux's VM doc for more details. 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 question will reach a larger audience. A question like this involving more discussion would be best posted on the mongodb-user group. See also our Technical Support page for additional support resources. Regards, |