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  1. Core Server
  2. SERVER-20104

WT high memory usage due to high amount of free memory accumulated by TCMalloc

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: Major - P3
    • Resolution: Done
    • Affects Version/s: None
    • Fix Version/s: None
    • Component/s: Performance, WiredTiger
    • Labels:
    • Operating System:
      ALL
    • Steps To Reproduce:
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      mongod --dbpath=d:\mongo --port=27200 --wiredTigerCacheSizeGB=3 --wiredTigerJournalCompressor=zlib --wiredTigerCollectionBlockCompressor=zlib

      User workload (Nick J)

      Show
      mongod --dbpath=d:\mongo --port=27200 --wiredTigerCacheSizeGB=3 --wiredTigerJournalCompressor=zlib --wiredTigerCollectionBlockCompressor=zlib User workload (Nick J)

      Description

      Environment:

      • Stand alone mongod
      • 3.1.6v
      • WiredTiger configured with zlib compression and 3GB cache size

      Observation/Issues:

      1. When running w/ 100 + threads, WT cache reached to 8GB (2.6 x original cache size).
      1. When running w/ 9 threads, WT cache reached to 5GB (1.6 x original cache size).

      Breakdown of the 5G memory highlight the followings:

      3 GB in the cache size (as expected)
      1.7 GB - Current_total_thread_cache_bytes (MB) (higher than expectation)
      0.45 GB - Total central_cache_free_bytes (MB) (higher than expectation)

      Problem: Our memory cache policy set for 1GB free, however the machine accumulate memory above this threshold.

        Attachments

        1. 100threads.html
          4.39 MB
        2. 100threads.png
          100threads.png
          104 kB
        3. 3.1.6-3Gcache.html
          4.44 MB
        4. buildInfo.txt
          1 kB
        5. collStatsLocalOplog.txt
          7 kB
        6. getCmdLineOpts.txt
          0.9 kB
        7. hostInfo.txt
          1 kB
        8. rsStatus.txt
          2 kB
        9. serverStatus.txt
          22 kB
        10. win_tcmalloc_agg.png
          win_tcmalloc_agg.png
          48 kB
        11. win_tcmalloc_default.png
          win_tcmalloc_default.png
          48 kB
        12. win_tcmalloc24.png
          win_tcmalloc24.png
          49 kB

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                Dates

                • Created:
                  Updated:
                  Resolved: