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  1. Core Server
  2. SERVER-31704

Periodic drops in throughput during checkpoints while waiting on schema lock

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      Run mix.js
      Set the following parameter:

      wiredTigerEngineRuntimeConfig:"file_manager=(close_handle_minimum=100,close_idle_time=300,close_scan_interval=30)"
      Show
      Run mix.js Set the following parameter: wiredTigerEngineRuntimeConfig:"file_manager=(close_handle_minimum=100,close_idle_time=300,close_scan_interval=30)"

      Periodic drops in throughput can be observed during checkpoints while running with an artificial workload and specific WiredTiger tuning parameters enabled.

      I've attached diagnostic.tar.gz that shows this behavior. At around 2017-10-20T20:10:08.587Z the following command was executed:

      db.adminCommand({setParameter: 1, wiredTigerEngineRuntimeConfig:"file_manager=(close_handle_minimum=100,close_idle_time=300,close_scan_interval=30)"});

      After reaching steady state, we see the following:

      Additionally, from perf, we can see that after making this parameter change, a single cpu core (12.5% of the total) is consistently fully utilized running eviction: 

      start_thread+0xffff017a586c80c5
__wt_thread_run+0xffff5458d1e2e016
__wt_evict_thread_run+0xffff5458d1e2e951

        1. checkpoint_lock_4.2.7.png
          176 kB
          Dmitry Agranat
        2. diagnostic.tar.gz
          69.76 MB
          Kelsey Schubert
        3. mix.js
          6 kB
          Kelsey Schubert
        4. no_checkpoint.png
          209 kB
          Dmitry Agranat
        5. periodic_drops.png
          339 kB
          Kelsey Schubert

            Assignee:
            brian.lane@mongodb.com Brian Lane
            Reporter:
            kelsey.schubert@mongodb.com Kelsey Schubert
            Votes:
            13 Vote for this issue
            Watchers:
            41 Start watching this issue

              Created:
              Updated:
              Resolved: