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  1. Core Server
  2. SERVER-22834

1.7x performance regression in random queries

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Details

    • Bug
    • Status: Closed
    • Major - P3
    • Resolution: Fixed
    • None
    • 3.3.6
    • WiredTiger
    • None
    • Fully Compatible
    • ALL

    Description

      • standalone, 3 GB cache
      • 10 GB data set, 10 M x 1 kB documents
      • 64 GB memory, SSD (but probably not relevant as data set should be in filesystem cache)
      • 100 threads doing random queries over data set, creating high cache pressure
      • observe ~1.7x performance regression in 3.2.3 compared to 3.0.9

      • A-B: 3.0.9
      • B-C: 3.2.3 (same data set)

                         3.0.9         3.2.3
       
      queries             82 k/s        48 k/s
      evictions           78 k/s        36 k/s
      walked             836 k/s      5813 k/s
      walked/eviction     11           160
      mutex calls        0.7 k/s        12 k/s
      

      It appears that a higher rate of pages walked per page evicted could be a significant factor, so possibly this is related to SERVER-22831, where pages walked for eviction also appeared to be a factor? (Note however that ticket requires a replica set, whereas this ticket is for a standalone mongod.)

      There is also a much higher rate of mutex calls.

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              sue.loverso@mongodb.com Susan LoVerso
              bruce.lucas@mongodb.com Bruce Lucas
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                Created:
                Updated:
                Resolved: