[SERVER-19932] Consider increasing wiredTiger cache size default Created: 13/Aug/15 Updated: 13/Aug/15 Resolved: 13/Aug/15 |
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| Status: | Closed |
| Project: | Core Server |
| Component/s: | WiredTiger |
| Affects Version/s: | None |
| Fix Version/s: | None |
| Type: | Improvement | Priority: | Major - P3 |
| Reporter: | Ben McCann | Assignee: | Unassigned |
| Resolution: | Duplicate | Votes: | 0 |
| Labels: | None | ||
| Remaining Estimate: | Not Specified | ||
| Time Spent: | Not Specified | ||
| Original Estimate: | Not Specified | ||
| Issue Links: |
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| Description |
WT cache uses the higher value of 50% of system memory or 1GB by default From what we've seen, MongoDB really needs the cache, but doesn't need much memory beyond that. We just increased to 85% of system memory and are getting dramatically better performance. Of course this may vary substantially by workload and user. However, I'd suggest that a higher default might be more appropriate for most users. It'd be interesting to see how much heap we're using to help inform this decision, but unfortunately db.serverStatus().extra_info.heap_usage_bytes is returning a negative number - |
| Comments |
| Comment by Ramon Fernandez Marina [ 13/Aug/15 ] |
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chengas123, our investigations led to a 60% default as described in Regards, |
| Comment by Bruce Lucas (Inactive) [ 13/Aug/15 ] |
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Regarding your question about heap usage - you can get more detailed heap statistics by using db.serverStatus( {tcmalloc:true}). Often virtual memory will be a reasonable indication of heap usage, although there are users of memory outside of heap, for example thread stacks, which could be a substantial amount of memory if you have a lot of connections. |