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Chapter 5. Memory

Read this chapter for an overview of the memory management features available in Red Hat Enterprise Linux, and how to use these management features to optimize memory utilization in your system.

5.1. Huge Translation Lookaside Buffer (HugeTLB)

Physical memory addresses are translated to virtual memory addresses as part of memory management. The mapped relationship of physical to virtual addresses is stored in a data structure known as the page table. Since reading the page table for every address mapping would be time consuming and resource-expensive, there is a cache for recently-used addresses. This cache is called the Translation Lookaside Buffer (TLB).
However, the TLB can only cache so many address mappings. If a requested address mapping is not in the TLB, the page table must still be read to determine the physical to virtual address mapping. This is known as a "TLB miss". Applications with large memory requirements are more likely to be affected by TLB misses than applications with minimal memory requirements because of the relationship between their memory requirements and the size of the pages used to cache address mappings in the TLB. Since each miss involves reading the page table, it is important to avoid these misses wherever possible.
The Huge Translation Lookaside Buffer (HugeTLB) allows memory to be managed in very large segments so that more address mappings can be cached at one time. This reduces the probability of TLB misses, which in turn improves performance in applications with large memory requirements.
Information about configuring the HugeTLB can be found in the kernel documentation: /usr/share/doc/kernel-doc-version/Documentation/vm/hugetlbpage.txt