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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
commit | 5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 (patch) | |
tree | a94efe259b9009378be6d90eb30d2b019d95c194 /Documentation/arm64/hugetlbpage.rst | |
parent | Initial commit. (diff) | |
download | linux-upstream/5.10.209.tar.xz linux-upstream/5.10.209.zip |
Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | Documentation/arm64/hugetlbpage.rst | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/Documentation/arm64/hugetlbpage.rst b/Documentation/arm64/hugetlbpage.rst new file mode 100644 index 000000000..a110124c1 --- /dev/null +++ b/Documentation/arm64/hugetlbpage.rst @@ -0,0 +1,43 @@ +.. _hugetlbpage_index: + +==================== +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 + ====== ======== ==== ======== === |