Analyzer lj-alloc-stats

# Name

lj-alloc-stats - Statistics for LuaJIT’s builtin Allocator (Directly allocated memory blocks larger than 128K will not be counted)

This analyzer monitors memory allocation patterns in LuaJIT’s built-in allocator within OpenResty and Kong applications. It captures three types of allocation data:

1. ‘used’ - currently allocated memory blocks (up to ~512KB)
2. ‘free’ - freed memory blocks available for reuse (up to ~6MB)
3. ‘segments’ - large memory segments allocated from system (128KB+) The analyzer generates histograms visualizing allocation size distributions, helping identify memory usage patterns and optimize Lua memory management. Note that extremely large direct allocations may bypass LuaJIT’s allocator entirely.

# Resource Category

Memory.

# Application Type & Technical Stack

• OpenResty
• Kong
• APISIX

# Command Line Syntax

The analyzer can be invoked directly on the command-line via the orxray utility from the openresty-xray-cli software package.

Alternatively, the analyzer can also be invoked manually or automatically on the web console UI of OpenResty XRay (like on the Advanced web page).

# PID is the target process PID.
orxray analyzer run lj-alloc-stats -p PID

# trace a shell command directly
orxray analyzer run lj-alloc-stats -c SHELL_CMD

# Tracing Multiple Processes

Not supported.

# Output Formats

• Histogram Bar Charts
• Plain Texts

# Output Example

{
  "distributions": {
    "segments": [
      {"count": 0, "key": "32768"},
      {"count": 10, "key": "131072"},
      {"count": 15, "key": "262144"},
      {"count": 18, "key": "524288"},
      {"count": 26, "key": "1048576"},
      {"count": 8, "key": "2097152"},
      {"count": 5, "key": "4194304"},
      {"count": 3, "key": "8388608"}
    ],
    "free": [
      {"count": 1070, "key": "32"},
      {"count": 278, "key": "64"},
      {"count": 1758, "key": "128"},
      {"count": 2885, "key": "256"},
      {"count": 2218, "key": "512"},
      {"count": 934, "key": "1024"},
      {"count": 1345, "key": "2048"},
      {"count": 423, "key": "4096"},
      {"count": 187, "key": "8192"},
      {"count": 266, "key": "32768"},
      {"count": 27, "key": "65536"},
      {"count": 22, "key": "131072"}
    ],
    "used": [
      {"count": 178, "key": "8"},
      {"count": 37270, "key": "32"},
      {"count": 32734, "key": "64"},
      {"count": 7169, "key": "128"},
      {"count": 8421, "key": "256"},
      {"count": 4924, "key": "512"},
      {"count": 1818, "key": "1024"},
      {"count": 4562, "key": "2048"},
      {"count": 2112, "key": "4096"},
      {"count": 939, "key": "8192"},
      {"count": 475, "key": "32768"}
    ]
  },
  "segments": {
    "min": 131072,
    "max": 14548992,
    "count": 85,
    "sum": 140115968
  },
  "used": {
    "min": 8,
    "max": 524296,
    "count": 100842,
    "sum": 83237768
  },
  "luajit_big_chunks": 790277,
  "luajit_GC_managed": 84028045,
  "free": {
    "min": 32,
    "max": 6259368,
    "count": 11502,
    "sum": 58973688
  }
}

# Author

The OpenResty Inc. Team.

# Copyright

Copyright (C) by OpenResty Inc. All rights reserved.