HugePages Calculator
Calculate the number of HugePages needed to back a given amount of memory, for a chosen huge page size.
Inputs
e.g. the shared_buffers or SGA size to back with huge pages
nr_hugepages
4,096
Allocated Memory
8,192.00MB
Rounding Overhead
0.00MB
sysctl Command
sysctl -w vm.nr_hugepages=4096
Step by step
Values used
Required Memory = 8,192 MB; HugePage Size = 2 MB (standard)
Huge pages required
nr_hugepages = ceil(required_memory_MB / hugepage_size_MB)
nr_hugepages
= 4,096
Allocated Memory
= 8,192.00 MB
Rounding Overhead
= 0.00 MB
sysctl Command
= sysctl -w vm.nr_hugepages=4096
How it works
HugePages reduce Translation Lookaside Buffer (TLB) misses for memory-intensive applications like databases by using much larger page sizes (2MB or 1GB) instead of the standard 4KB page. The number of huge pages required is the required memory divided by the huge page size, rounded up, since HugePages must be allocated in whole units. Any excess from rounding is memory reserved but unused by the target application.
Formula
Huge pages required
nr_hugepages = ceil(required_memory_MB / hugepage_size_MB)
- M
- required memory in MB
- H
- huge page size in MB
Frequently Asked Questions
Why use HugePages instead of the default 4KB pages?
Larger pages mean fewer page table entries are needed to map the same amount of memory, which reduces TLB misses and page table walk overhead — a meaningful performance gain for applications with large, actively-used memory regions like database shared buffers.
What is the difference between 2MB and 1GB huge pages?
2MB pages are the standard HugeTLB size supported on virtually all x86_64 systems and can be allocated dynamically at runtime. 1GB 'gigantic' pages need CPU and kernel support, are typically reserved at boot time via a kernel parameter, and are used for very large, static memory regions.
Once allocated, can HugePages memory be used by other applications?
No — memory reserved for HugePages is removed from the normal page allocator and can only be used by applications explicitly requesting huge pages, so over-allocating wastes RAM that regular processes could have used.