Network stack
IRPStackSize
A file-server setting that has nothing to do with gaming latency
Last updated
Does increasing IRPStackSize improve network performance?
IRPStackSize controls how many stack locations Windows allocates in I/O request packets used by the SMB file server service. It exists to accommodate deep driver stacks on machines with layered filter drivers, and its documented failure mode is a specific file-sharing error. It is not a gaming or latency setting, despite appearing in a great many gaming tweak lists.
Registry location and values
IRPStackSize
- Location
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters- Value name
IRPStackSize- Type
REG_DWORD- Default
- 15 on current Windows versions
| Value | What it does |
|---|---|
11-50 | Valid range. Raise only when troubleshooting a specific SMB failure. |
What Windows actually does with this
An I/O request packet carries a stack location for each driver in the stack that will process it. LanmanServer allocates a fixed number in advance. With enough layered filter drivers -- antivirus, backup, encryption -- the allocation can be too small, and the server service fails to start or returns a not-enough-server-storage error.
What it affects
The SMB file server component only. If you are not sharing folders from this machine, nothing on it is reading this value in a way you will notice.
Is it worth changing?
Cargo cult. It appears in gaming tweak lists because it lives under a key with "Server" in the name and takes a number that can be raised, which reads like a buffer you can enlarge for more performance. It governs SMB file sharing. Raise it if you are chasing a documented SMB error and not otherwise. This is the clearest example on this site of a tweak that persists purely because it has been copied between guides for twenty years.
What can go wrong
Low but non-zero: the value allocates non-paged pool. Setting it far above what is needed wastes kernel memory for nothing.
How to undo it
Delete the value and restart. It is absent on a default installation.
Create a System Restore Point before editing the registry. Every setting on this page is reversible, but a restore point is the difference between undoing one change and reinstalling Windows.
Which Windows versions this applies to
All modern Windows versions.
IRPStackSize: common questions
Why is it in so many gaming guides?
It has been copied forward from Windows NT-era tuning lists. Nobody re-checked what LanmanServer does. It is a good illustration of why a registry tweak appearing in many guides is not evidence that it works.