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  1. WiredTiger
  2. WT-7182

Long latencies for some requests with large HS and heavy update workload

    • Type: Icon: Bug Bug
    • Resolution: Won't Fix
    • Priority: Icon: Major - P3 Major - P3
    • None
    • Affects Version/s: None
    • Component/s: None
    • 8
    • Storage - Ra 2021-06-28, Storage - Ra 2021-07-12, Storage - Ra 2021-07-26

      Some requests show latencies of more than 10 seconds when running a long workload (~5 million updates) with the stable timestamp pinned.

      I reran the test workload from PM-1844 on 4.4.4-rc0 to see how it performs with the fix for WT-6924. The test workload has a long "grow" phase, which performs a lot of updates (with a few inserts and deletes) designed to grow the WT history store.  Before the fix for WT-6924, this phase cause the WT cache to vastly exceed its configured size limits which also caused many updates to have high latencies.  

      In this test, the WT cache adheres to its configured size, and update throughput looks more consistent through much of the test.  But by the end of the test we are still seeing much lower performance and some individual operations (~9000) have latencies > 1 second.

      I'll attach data.tgz with the FTDC data and mongod log file.

        1. 07_v2_flame_02.png
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          Alison Felizzi
        2. b6_7_hits_v2_new.png
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          Alison Felizzi
        3. Batch6_7.png
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          Alison Felizzi
        4. Batch7_02.png
          4.19 MB
          Alison Felizzi
        5. data.tgz
          28.36 MB
          Keith Smith
        6. evergreen_vol.png
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          Alison Felizzi
        7. file_level_stats_hs.png
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          Alison Felizzi
        8. file_level_stats_idx34.png
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          Alison Felizzi
        9. file_level_stats_idx35.png
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          Alison Felizzi
        10. file_level_stats_idx36.png
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          Alison Felizzi
        11. file_level_stats_idx41.png
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          Alison Felizzi
        12. file_level_stats_idx43.png
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          Alison Felizzi
        13. fs_chedkpoint.png
          186 kB
          Alison Felizzi
        14. heatmap_latency_a_b.png
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          Alison Felizzi
        15. hs_flame_graph_evict.png
          358 kB
          Alison Felizzi
        16. hs_noaws.png
          165 kB
          Alison Felizzi
        17. io_flame.png
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          Alison Felizzi
        18. latency flame.png
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          Alison Felizzi
        19. Screen Shot 2021-02-09 at 10.23.48 PM.png
          195 kB
          Keith Smith
        20. Screen Shot 2021-07-15 at 12.53.56 pm.png
          135 kB
          Alison Felizzi
        21. t2_hs_overview.png
          270 kB
          Alison Felizzi
        22. ts_hs_eviction.png
          173 kB
          Alison Felizzi

            Assignee:
            alison.felizzi@mongodb.com Alison Felizzi (Inactive)
            Reporter:
            keith.smith@mongodb.com Keith Smith
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            Watchers:
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              Created:
              Updated:
              Resolved: