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Description

Same as system.jemalloc_bins but with one row per (arena, bin) instead of aggregating over arenas. Slabs belong to a single arena, so this table locates fragmentation in a specific arena (including the dedicated MergeTree metadata, JIT and cache arenas) and joins to system.jemalloc_sampled_allocations on both arena and size class.

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Columns

  • arena (UInt32) — Index of the arena. Joins to system.jemalloc_sampled_allocations.arena.
  • purpose (String) — Purpose of a dedicated long-lived arena: ‘mergetree’ (part and table metadata), ‘jit’, ‘cache’. Empty for general-purpose arenas. Dedicated arenas hold long-lived allocations by design; fragmentation reports usually exclude them.
  • index (UInt16) — Index of the bin ordered by size.
  • large (UInt8) — True for large allocations and False for small.
  • size (UInt64) — Size of allocations in this bin.
  • allocations (Int64) — Number of allocations.
  • deallocations (Int64) — Number of deallocations.
  • nregs (Int64) — Number of regions per slab.
  • curslabs (Int64) — Current number of slabs.
  • curregs (Int64) — Current number of regions for this size class.
  • slab_size (UInt64) — Size of each slab in bytes. Zero for large size classes, which are not slab-based.
  • nonfull_slabs (Int64) — Current number of slabs that contain at least one free region. Zero for large size classes.
Aliases:
  • availregs — Alias for nregs * curslabs.
  • util — Alias for curregs / availregs.
  • waste — Alias for greatest((curslabs * slab_size) - (curregs * size), 0).
Last modified on September 9, 2026