1.1 HugePages 介绍
HugePages is afeature integrated into the Linux kernel with release 2.6. This featurebasically provides the alternative to the 4K page size (16Kfor IA64) providing bigger pages.
（1） Page Table: A page table is thedata structure of a virtual memory system in an operating system to store themapping between virtual addresses and physical addresses. This means that on avirtual memory system, the memory is accessed by first accessing a page tableand then accessing the actual memory location implicitly.
（2） TLB: A Translation LookasideBuffer (TLB) is a buffer (or cache) in a CPU that contains parts ofthe page table. This is a fixed size buffer being used to do virtual addresstranslation faster.
（3） hugetlb: This is an entryin the TLB that points to a HugePage (a large/big page larger than regular 4Kand predefined in size). HugePages are implemented via hugetlb entries, i.e. wecan say that a HugePage is handled by a "hugetlb page entry". The'hugetlb" term is also (and mostly) used synonymously with a HugePage(See Note261889.1). In this document the term "HugePage" is going to beused but keep in mind that mostly "hugetlb" refers to the sameconcept.
（4） hugetlbfs: This is a newin-memory filesystem like tmpfs and is presented by 2.6 kernel. Pages allocatedon hugetlbfs type filesystem are allocated in HugePages.
1.2 常见的错误概念
WRONG: HugePages is a method to be able to use large SGA on 32-bit VLM systems
RIGHT: HugePages is a method to have larger pages where it is useful for working with very large memory. It is both useful in 32- and 64-bit configurations
WRONG: HugePages cannot be used without USE_INDIRECT_DATA_BUFFERS
RIGHT: HugePages can be used without indirect buffers. 64-bit systems does not need to use indirect buffers to have a large buffer cache for the RDBMS instance and HugePages can be used there too.
WRONG: hugetlbfs means hugetlb
RIGHT: hugetlbfs is a filesystem type **BUT** hugetlb is the mechanism employed in the back where hugetlb can be employed WITHOUT hugetlbfs
WRONG: hugetlbfs means hugepages
RIGHT: hugetlbfs is a filesystem type **BUT** HugePages is the mechanism employed in the back (synonymously with hugetlb) where HugePages can be employed WITHOUT hugetlbfs.