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Description

One row per live sampled allocation from the jemalloc heap profiler; reading the table flushes a fresh heap profile. Only threads with the profiler armed contribute (jemalloc_enable_profiler setting or jemalloc_enable_global_profiler config); each row represents roughly weight similar allocations.

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Columns

  • trace (Array(UInt64)) — Addresses of the allocating backtrace, leaf frame first (same convention as system.trace_log.trace). Symbolize with addressToSymbol and demangle (requires allow_introspection_functions).
  • age_ns (UInt64) — Time in nanoseconds the allocation has been alive, relative to the moment the profile was flushed.
  • size (UInt64) — Requested allocation size in bytes.
  • usize (UInt64) — Usable size in bytes, i.e. the size class the request was rounded up to.
  • size_class (UInt16) — Index of the size class. Joins to system.jemalloc_bins.index for small size classes.
  • arena (UInt32) — Index of the arena the allocation was served from.
  • thr_uid (UInt64) — jemalloc-internal unique id of the allocating thread.
  • sample_interval (UInt64) — Average number of allocated bytes between samples, taken from the profile header. The same for all rows.
Aliases:
  • alloc_time — Alias for now() - intDiv(age_ns, 1000000000).
  • weight — Alias for 1 / (1 - exp((-usize) / sample_interval)).
Last modified on September 9, 2026