windbg-user-virtual-memory-exhaustion

Use when a native app, service, or user-mode driver host allocation fails; distinguish VA exhaustion, fragmentation, and commit pressure. Not for managed .NET heap growth, proving a leak from one snapshot, or corruption.

Virtual Memory Exhaustion

Load windbg-diagnostic-method first if it is not already loaded in this conversation, and apply it throughout for evidence ranking, hypothesis testing, confidence calibration, independent review, and report validation. This skill adds the bug-family-specific commands and evidence requirements.

Detection

Investigate E_OUTOFMEMORY (0x8007000E), STATUS_NO_MEMORY (0xC0000017), bad_alloc, or failed heap/virtual allocations in an application, service, or user-mode driver host (including UMDF). Record the actual API, requested size/alignment, architecture, flags, and error. Free physical RAM does not rule out insufficient virtual address space, commit pressure, or applicable limits.

Workflow

1. Examine the process VA map

!address -summary
!address
!heap -s

Compare available regions with the attempted allocation's contiguous range and alignment requirements. Distinguish reserved, committed, free, image, mapped, stack, and heap ranges. A large reservation consumes VA without committing its entire range. Heap internals may require more than the user's requested bytes.

Report unavailable pages/map data rather than inferring completeness from a limited dump.

2. Separate pressure mechanisms

Mechanism	Evidence needed
VA exhaustion	Process address range/architecture and little usable free VA
Fragmentation	Free space exists, but no suitable contiguous/aligned region
System commit pressure	Commit usage/limit near the failure, not just free RAM
Process/job memory limit	Actual configured limit and relevant usage/accounting
Allocation policy/API failure	API-specific constraints, flags, or allocator policy

Use contemporaneous system memory counters or an appropriate live/kernel session for system commit data. A process PEB is not a documented MaximumCommit source. A process's committed bytes alone do not establish a system-wide or job limit.

For 32-bit targets inspect /LARGEADDRESSAWARE and the host architecture; 2 GB versus up to 4 GB depends on those settings. Verify current documented limits for the target Windows version and architecture instead of applying one 64-bit limit to every system.

3. Identify dominant consumers

!address -f:Heap
!address -f:Stack
!heap -stat -h <heap-address>

Use !address -? and !heap -? for allocator/version-specific support. Classify dominant heaps, stacks, mappings, images, and reserved arenas. Large or numerous allocations are not automatically leaks: map them to cache policy, owners, workload, and expected lifetimes.

4. Establish growth with history

Collect authorized time-series counters, repeated comparable snapshots, or allocation/free tracing across the workload. Compare warm-up with steady-state behavior and verify whether memory is reclaimed when work finishes.

One snapshot plus process uptime cannot prove a leak rate. For a suitable user-mode recording use windbg-user-ttd-reverse-debugging-triage; for damaged allocations use windbg-user-heap-corruption-investigation instead.

Fix patterns

• Bound caches by an appropriate size/cost policy and verify eviction. Define the lifetime of any references returned before eviction.
• Match VirtualAlloc reservations with the correct VirtualFree release contract; distinguish decommit from release.
• Use RAII to release resources on all supported exit/error paths.
• Reduce large contiguous allocation requirements where the design permits.
• Do not blindly increase limits or stack reservations before finding the pressure source, and do not convert a failed allocation into a silent success.

Validation

Name the failing allocation and pressure mechanism, identify the consumer with evidence, and exercise the remedy through warm-up, sustained load, and cleanup. Verify memory remains bounded or the intended allocation succeeds under the required constraints. Document configured system/job limits separately.

References

• Address extension
• Heap extension
• Windows memory limits
• Large-address-aware linker option
• VirtualFree

Feedback

Follow FEEDBACK.md and submit reviewed, sanitized feedback to WinDbg-Feedback. Include windbg-user-virtual-memory-exhaustion and the package version from plugin.json; no automatic dump or memory-content upload.