1.. _hugetlbpage_index: 2 3==================== 4HugeTLBpage on ARM64 5==================== 6 7Hugepage relies on making efficient use of TLBs to improve performance of 8address translations. The benefit depends on both - 9 10 - the size of hugepages 11 - size of entries supported by the TLBs 12 13The ARM64 port supports two flavours of hugepages. 14 151) Block mappings at the pud/pmd level 16-------------------------------------- 17 18These are regular hugepages where a pmd or a pud page table entry points to a 19block of memory. Regardless of the supported size of entries in TLB, block 20mappings reduce the depth of page table walk needed to translate hugepage 21addresses. 22 232) Using the Contiguous bit 24--------------------------- 25 26The architecture provides a contiguous bit in the translation table entries 27(D4.5.3, ARM DDI 0487C.a) that hints to the MMU to indicate that it is one of a 28contiguous set of entries that can be cached in a single TLB entry. 29 30The contiguous bit is used in Linux to increase the mapping size at the pmd and 31pte (last) level. The number of supported contiguous entries varies by page size 32and level of the page table. 33 34 35The following hugepage sizes are supported - 36 37 ====== ======== ==== ======== === 38 - CONT PTE PMD CONT PMD PUD 39 ====== ======== ==== ======== === 40 4K: 64K 2M 32M 1G 41 16K: 2M 32M 1G 42 64K: 2M 512M 16G 43 ====== ======== ==== ======== === 44