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  1. Core Server
  2. SERVER-26040

High CPU/IOWAIT in MongoDB 3.2.9

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Details

    • Bug
    • Status: Closed
    • Major - P3
    • Resolution: Works as Designed
    • 3.2.9
    • None
    • None
    • None
    • ALL

    Description

      After upgrading a replica set to 3.2.9, I am seeing:

      • increased CPU usage on the two hosts that have SSD's
      • increased CPU and IOWAIT on the host that has regular HDDs (in software RAID1, if it makes any difference)

      The workload hasn't changed before/after the upgrade (about 40-60 inserts / 1-2 queries / 0 updates / 0 deletes – per second)

      The configuration also hasn't changed, I've been running WiredTiger before as well.

      The storage configuration is configured as follows:

      storage:
        dbPath: /var/lib/mongodb
        directoryPerDB: true
        journal:
          enabled: true
        engine: "wiredTiger"
        wiredTiger:
              engineConfig: 
                  journalCompressor: zlib
              collectionConfig: 
                  blockCompressor: zlib 
              indexConfig:
                  prefixCompression: true
      

      I've attached diagnostic.data as requested and some munin charts that show the difference before/after.

      Seemingly related issues:

      Let me know if there's anything else I can do to help.

      Attachments

        1. diagnostic.data.tar
          101.70 MB
        2. disk_utilization.png
          disk_utilization.png
          23 kB
        3. hdd1-cpu-week.png
          hdd1-cpu-week.png
          25 kB
        4. hdd1-diskstats_utilization-week.png
          hdd1-diskstats_utilization-week.png
          31 kB
        5. ssd1-cpuspeed-week.png
          ssd1-cpuspeed-week.png
          35 kB
        6. ssd1-cpu-week.png
          ssd1-cpu-week.png
          22 kB
        7. ssd2-cpuspeed-week.png
          ssd2-cpuspeed-week.png
          37 kB
        8. ssd2-cpu-week.png
          ssd2-cpu-week.png
          21 kB

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              kelsey.schubert@mongodb.com Kelsey T Schubert
              emilburzo Emil Burzo
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              Dates

                Created:
                Updated:
                Resolved: