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  1. Core Server
  2. SERVER-31380

Add metrics related to tcmalloc acquiring and decommitting memory from system

    • Fully Compatible
    • v3.4, v3.2
    • Platforms 2017-11-13

      From time to time tcmalloc acquires memory from the system using mmap, and returns it to the system using madvise. These can be expensive operations, and they hold a lock so they can create a bottleneck. There aren't adequate metrics to diagnose issues related to this, and to assess the effect of making changes such as enabling TCMALLOC_AGGRESSIVE_DECOMMIT. The following could be helpful:

      • number of mmap operations to acquire memory
      • number of bytes acquired
      • cumulative time spent in such operations
      • number of madvise oeprations to release memory
      • number of bytes released
      • cumulative time spent in such operations
      • number of bytes allocated using decommitted memory (which kernel then must re-commit)

            mark.benvenuto@mongodb.com Mark Benvenuto
            bruce.lucas@mongodb.com Bruce Lucas (Inactive)
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