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  1. Core Server
  2. SERVER-16941

Cache can grow indefinitely under WiredTiger

    • Type: Icon: Bug Bug
    • Resolution: Done
    • Priority: Icon: Major - P3 Major - P3
    • None
    • Affects Version/s: 2.8.0-rc5
    • Component/s: Storage, WiredTiger
    • Labels:
    • ALL

      During a 20-minute run with heavy mixed workload the cache was observed to grow on occasion (2 runs out of about 30) to almost 9 GB, compared to a configured value of 5 GB. An assortment of potentially relevant metrics:

      • at point B the checkpoint enters the second phase where "range of ids pinned" grows.
      • at this point bytes in cache starts growing, and continues growing, apparently indefinitely.
      • at C we begin to page performance declines correspondingly.
      • if run continued beyond 20 minutes growth would have likely resulted on being killed by OOM killer.
      • checkpoint is running longer than it did in runs that didn't experience the issue - typically that third checkpoint completed before the end of the run.
      • the spike in reported cached bytes at A, without corresponding increase in VM, is probably the apparent accounting error from SERVER-16881, which is seen to occur frequently in these runs. However the increase starting at B that is the subject of this ticket is accompanied by an increase in VM, so is likely an unrelated issue.

            bruce.lucas@mongodb.com Bruce Lucas (Inactive)
            bruce.lucas@mongodb.com Bruce Lucas (Inactive)
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