Tuning Jemalloc 5

jemalloc5.rb

# Inspiration: https://twitter.com/wgjordan/status/1440574986264006659

jemalloc_conf = {
  # Maximum number of arenas to use for automatic multiplexing of threads and arenas.
  # The default is four times the number of CPUs, or one if there is a single CPU.
  narenas: 2,

  # Enabling jemalloc background threads generally improves the tail latency for application threads,
  # since unused memory purging is shifted to the dedicated background threads.
  # In addition, unintended purging delay caused by application inactivity is avoided with background threads.
  #
  # Suggested: background_thread:true when jemalloc managed threads can be allowed.
  background_thread: true, # default false

  # Transparent hugepage (THP) mode.
  # Settings "always", "never" and "default" are available if THP is supported by the operating system.
  # The "always" setting enables transparent hugepage for all user memory mappings with MADV_HUGEPAGE;
  # "never" ensures no transparent hugepage with MADV_NOHUGEPAGE; the default setting "default" makes no changes.
  thp: 'never',

  # Decay time determines how fast jemalloc returns unused pages back to the operating system,
  # and therefore provides a fairly straightforward trade-off between CPU and memory usage.
  # Shorter decay time purges unused pages faster to reduces memory usage
  # (usually at the cost of more CPU cycles spent on purging), and vice versa.
  #
  # Suggested: tune the values based on the desired trade-offs.
  dirty_decay_ms: 1_000, # Default 10_000
  muzzy_decay_ms: 0 # Default 10_000
}.map {|x| x.join(':')}.join(',')

# MALLOC_CONF="narenas:2,background_thread:true,thp:never,dirty_decay_ms:1000,muzzy_decay_ms:0"