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  1. Core Server
  2. SERVER-18315

Throughput drop during transaction pinned phase of checkpoints under WiredTiger

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: Major - P3
    • Resolution: Fixed
    • Affects Version/s: 3.0.2
    • Fix Version/s: 3.0.4, 3.1.3
    • Component/s: WiredTiger
    • Labels:
    • Backwards Compatibility:
      Fully Compatible
    • Operating System:
      ALL
    • Backport Completed:

      Description

      • YCSB 30M documents, 10 fields, ~1kB/document, total ~30GB
      • 50/50 read/update workload
      • 40 GB cache, 128 GB memory, 32 CPUs
      • slow SSD disk (~80-100 MB/s)
      • no journal (to simplify the situation)
      • per mongostat, cache is at 100% utilization, 80% dirty pretty much throughout the test.

      During each checkpoint while a transaction id is pinned for the checkpoint throughput falls by an order of magnitude (but not to 0). This is accompanied by activity in the "checkpoint blocked eviction" counter. This is seen in B-C, F-G, J-K below:

      Similar test with a larger cache (the default 64GB) also shows this issue.

      Note: this is the same test as reported in SERVER-18314; opening two separate tickets to track what may be separate issues.

        Attachments

        1. try-13.png
          try-13.png
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        2. try-15.png
          try-15.png
          127 kB
        3. try-15-gdb.png
          try-15-gdb.png
          372 kB
        4. try-23.png
          try-23.png
          114 kB
        5. try-25.png
          try-25.png
          116 kB

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                • Created:
                  Updated:
                  Resolved: