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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)"

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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)"

    Description

      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
      

      Attachments

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

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              brian.lane@mongodb.com Brian Lane
              kelsey.schubert@mongodb.com Kelsey T Schubert
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                Created:
                Updated:
                Resolved: