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Diffstat (limited to 'Documentation/arm64/hugetlbpage.txt')
| -rw-r--r-- | Documentation/arm64/hugetlbpage.txt | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/Documentation/arm64/hugetlbpage.txt b/Documentation/arm64/hugetlbpage.txt new file mode 100644 index 0000000000000..cfae87dc653b3 --- /dev/null +++ b/Documentation/arm64/hugetlbpage.txt @@ -0,0 +1,38 @@ +HugeTLBpage on ARM64 +==================== + +Hugepage relies on making efficient use of TLBs to improve performance of +address translations. The benefit depends on both - + + - the size of hugepages + - size of entries supported by the TLBs + +The ARM64 port supports two flavours of hugepages. + +1) Block mappings at the pud/pmd level +-------------------------------------- + +These are regular hugepages where a pmd or a pud page table entry points to a +block of memory. Regardless of the supported size of entries in TLB, block +mappings reduce the depth of page table walk needed to translate hugepage +addresses. + +2) Using the Contiguous bit +--------------------------- + +The architecture provides a contiguous bit in the translation table entries +(D4.5.3, ARM DDI 0487C.a) that hints to the MMU to indicate that it is one of a +contiguous set of entries that can be cached in a single TLB entry. + +The contiguous bit is used in Linux to increase the mapping size at the pmd and +pte (last) level. The number of supported contiguous entries varies by page size +and level of the page table. + + +The following hugepage sizes are supported - + + CONT PTE PMD CONT PMD PUD + -------- --- -------- --- + 4K: 64K 2M 32M 1G + 16K: 2M 32M 1G + 64K: 2M 512M 16G |