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jemalloc_bins

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Autogenerated from ClickHouse system tables

Description

Contains information about memory allocations done via jemalloc allocator in different size classes (bins) aggregated from all arenas. These statistics might not be absolutely accurate because of thread local caching in jemalloc.

For small size classes the slab columns (slab_size, nonfull_slabs and the waste alias) measure memory lost to slab fragmentation.

Columns

  • 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).

Examples

Find the sizes of allocations that contributed the most to the current overall memory usage.

SELECT
    *,
    allocations - deallocations AS active_allocations,
    size * active_allocations AS allocated_bytes
FROM system.jemalloc_bins
WHERE allocated_bytes > 0
ORDER BY allocated_bytes DESC
LIMIT 10
┌─index─┬─large─┬─────size─┬─allocactions─┬─deallocations─┬─active_allocations─┬─allocated_bytes─┐
│    82 │     1 │ 50331648 │            1 │             0 │                  1 │        50331648 │
│    10 │     0 │      192 │       512336 │        370710 │             141626 │        27192192 │
│    69 │     1 │  5242880 │            6 │             2 │                  4 │        20971520 │
│     3 │     0 │       48 │     16938224 │      16559484 │             378740 │        18179520 │
│    28 │     0 │     4096 │       122924 │        119142 │               3782 │        15491072 │
│    61 │     1 │  1310720 │        44569 │         44558 │                 11 │        14417920 │
│    39 │     1 │    28672 │         1285 │           913 │                372 │        10665984 │
│     4 │     0 │       64 │      2837225 │       2680568 │             156657 │        10026048 │
│     6 │     0 │       96 │      2617803 │       2531435 │              86368 │         8291328 │
│    36 │     1 │    16384 │        22431 │         21970 │                461 │         7553024 │
└───────┴───────┴──────────┴──────────────┴───────────────┴────────────────────┴─────────────────┘
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