[Bug 59476] New: WINE_RESERVE VM region count grows unboundedly (~20k regions/min), exhausting system memory

[WineHQ Bugzilla]

http://bugs.winehq.org/show_bug.cgi?id=59476

            Bug ID: 59476
           Summary: WINE_RESERVE VM region count grows unboundedly (~20k
                    regions/min), exhausting system memory
           Product: Wine
           Version: 11.0
          Hardware: x86-64
                OS: MacOS
            Status: UNCONFIRMED
          Severity: major
          Priority: P2
         Component: -unknown
          Assignee: [e-mail]
          Reporter: [e-mail]

Created attachment 80465
  --> http://bugs.winehq.org/attachment.cgi?id=80465
vmmap and memory growth over time.

On macOS (Apple Silicon, Rosetta 2), running applications that perform frequent
VirtualAlloc/VirtualFree cycles (such as .NET applications) causes Wine's
WINE_RESERVE address space to fragment into an ever-growing number of mach VM
regions. The macOS kernel never coalesces adjacent freed regions, so the region
count grows indefinitely. Each region carries kernel metadata overhead, and the
cumulative overhead eventually exhausts system memory.

Steps to reproduce:
1. Run SolidWorks 2025 (or any .NET-heavy application) on macOS with Wine 11.0
2. Run: vmmap -summary <pid>  (repeating every 30 seconds)
3. Observe WINE_RESERVE region count growing continuously

Measured data (SolidWorks 2025, macOS 26.3, Apple Silicon, 16GB RAM):

At launch (~30s):
  WINE_RESERVE: 8.0G virtual, 21,748 regions
  VM_ALLOCATE:  unknown, ~3,094 regions
  Physical footprint: 2.4G

After 5 minutes:
  WINE_RESERVE: 8.0G virtual, 113,059 regions (+91,311 new regions)
  VM_ALLOCATE:  2.0G virtual, 29,892 regions
  Total regions: 176,901
  Physical footprint: 9.7G

After 15 minutes:
  WINE_RESERVE: 8.0G virtual, 113,909 regions
  VM_ALLOCATE:  9.9G virtual, 159,877 regions
  Total regions: 307,327
  Physical footprint: 17.7G

Region growth rate: approximately 20,000 new regions per minute.

The WINE_RESERVE virtual size stays constant at 8GB — it is not allocating more
memory. It is fragmenting the existing reservation into more and more tiny mach
VM regions. macOS tracks kernel metadata per region, and at ~300,000 regions
the overhead triggers "Your system has run out of application memory."

On Linux this is not a problem because the kernel can coalesce adjacent mmap
regions with identical protections. macOS mach_vm_allocate regions are
permanent and never merge.

Full vmmap -summary output is attached.

System: macOS 26.3, Apple Silicon (M-series, 16GB RAM), Wine 11.0 stable,
Rosetta 2 translation

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[Bug 59476] WINE_RESERVE VM region count grows unboundedly (~20k regions/min), exhausting system memory

[WineHQ Bugzilla]

http://bugs.winehq.org/show_bug.cgi?id=59476

[e-mail] changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Hardware|x86-64                      |arm

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