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  1. Core Server
  2. SERVER-19932

Consider increasing wiredTiger cache size default

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    Details

    • Type: Improvement
    • Status: Closed
    • Priority: Major - P3
    • Resolution: Duplicate
    • Affects Version/s: None
    • Fix Version/s: None
    • Component/s: WiredTiger
    • Labels:
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      Description

      storage:
         wiredTiger:
            engineConfig:
               cacheSizeGB: <number>
      

      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 - SERVER-19931

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