Skip to content

memory-observability-process-breakdown.md

Latest commit

 

History

History
52 lines (42 loc) · 1.7 KB

memory-observability-process-breakdown.md

File metadata and controls

52 lines (42 loc) · 1.7 KB

Memory Observability: Process Breakdown And Unattributed RSS

This group explains the process-level attribution that sits above individual subsystem counters.

Observability fields and metrics:

  • /_mem.process_breakdown
  • /_details.runtime.memory.process_breakdown
  • process.memory.rss.anon.bytes
  • process.memory.rss.file.bytes
  • process.memory.rss.shmem.bytes
  • process.memory.js_managed.bytes
  • process.memory.js_external_non_array_buffers.bytes
  • process.memory.unattributed.bytes
  • process.memory.unattributed_anon.bytes

Where implemented:

  • src/runtime_memory.ts
    • parseLinuxStatusRssBreakdown(...)
    • readLinuxStatusRssBreakdown(...)
    • buildProcessMemoryBreakdown(...)
  • src/app_core.ts
    • snapshot composition
    • metrics emission

Platform behavior:

  • on Linux, the breakdown uses /proc/self/status fields:
    • RssAnon
    • RssFile
    • RssShmem
  • on other platforms, the endpoint still reports unattributed_rss_bytes, but the anon/file/shmem fields are null

Interpretation rules:

  • js_managed_bytes is heap_used_bytes + external_bytes
  • mapped_file_bytes is the tracked file-backed mmap footprint from runtime caches
  • sqlite_runtime_bytes is the current SQLite allocator usage from sqlite3_status64() when available
  • unattributed_rss_bytes is the remaining RSS after subtracting:
    • JS-managed bytes
    • tracked mapped-file bytes
    • tracked SQLite runtime bytes
  • unattributed_anon_bytes is the remaining Linux anonymous RSS after subtracting:
    • JS-managed bytes
    • tracked SQLite runtime bytes

These unattributed values are intentionally conservative approximations. They are useful as "what is still unexplained?" signals, not exact ownership maps.