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  1. Core Server
  2. SERVER-31417

Improve tcmalloc when decommitting large amounts of memory

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Details

    • Product Performance
    • Dev Tools 2019-05-06, Dev Tools 2019-04-22

    Description

      tcmalloc may occasionally release large amounts of pageheap free memory to the kernel by calling madvise. This can take seconds when the amount of memory involved is many GB. A tcmalloc internal lock is held while this happens, so this can potentially stall many threads, causing widespread latency spikes.

      There is no direct metric that diagnoses this (SERVER-31380 would provide that), but it can be indirectly inferred to be a likely cause from the following:

      • tcmalloc pageheap free memory decreases to near zero
      • tcmalloc unmapped memory increases by a corresponding amount
      • resident memory decreases by the same amount
      • system free memory increases by that amount

      Attachments

        Issue Links

          duplicates

          Bug - A problem which impairs or prevents the functions of the product. SERVER-34027 Production issue under high load.

          • Major - P3 - Major loss of function.
          • Closed
          is duplicated by

          Bug - A problem which impairs or prevents the functions of the product. SERVER-34027 Production issue under high load.

          • Major - P3 - Major loss of function.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. SERVER-37541 MongoDB Not Returning Free Space to OS

          • Major - P3 - Major loss of function.
          • Closed
          is related to

          Bug - A problem which impairs or prevents the functions of the product. SERVER-33296 Excessive memory usage due to heap fragmentation

          • Major - P3 - Major loss of function.
          • Backlog
          related to

          Improvement - An improvement or enhancement to an existing feature or task. SERVER-31380 Add metrics related to tcmalloc acquiring and decommitting memory from system

          • Major - P3 - Major loss of function.
          • Closed
          mentioned in

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              backlog-server-perf Backlog - Performance Team
              bruce.lucas@mongodb.com Bruce Lucas (Inactive)
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              Dates

                Created:
                Updated: