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.
Sources
Related settings
Guides that cover this setting
Every change JINSHI PC Tweaks can make is listed on the complete tweak list, and the product itself is described on PC Tweaks for gaming.
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