Memory not released after indexing: 20GB+ RSS for 5MB of indexed data

[fxfxfx123]

Summary

After indexing a small project (65 files, 1.3MB, 2509 nodes), codebase-memory-mcp retains 20GB+ RSS on a 32GB Windows machine. Memory grows monotonically and is never released to the OS.

Environment

• OS: Windows 11, i7-12700 (20 cores), 32GB RAM
• CBM Version: 0.8.1
• Project: 65 Markdown files, 1.3MB, 2509 nodes

Root Cause (from source code)

1. mimalloc abandoned-thread arenas not purged (mem.c missing mi_option_abandoned_thread_purge)
2. Default worker count uses all 20 cores, each with its own mimalloc arena
3. DEFAULT_RAM_FRACTION=0.5 means 16GB budget, no pressure to release

Observed memory

Without fix: 20GB+ RSS, growing 600MB/min, never releases
With workaround (CBM_WORKERS=1): 13MB stable

Fix

PR #831: #831

• Enable mi_option_abandoned_thread_purge in mem.c
• Lower DEFAULT_RAM_FRACTION from 0.5 to 0.25
• Cap initial worker count at 8 in system_info.c

Workaround

Set CBM_WORKERS=1 in MCP env config and run: codebase-memory-mcp config set auto_index false

[DeusData]

Thanks for the Windows memory-retention report and the before/after numbers. Triage: high-priority stability/performance issue under #593, with Windows impact.

This overlaps the memory-pressure work in #752/#685 but is more specific about post-index RSS retention and mimalloc worker-thread arenas. I see #833 is open against this; review should check that memory is actually returned after indexing without just hiding the issue by reducing worker parallelism too aggressively.