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author | Thomas Gleixner <tglx@linutronix.de> | 2019-07-28 22:22:40 +0200 |
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committer | Thomas Gleixner <tglx@linutronix.de> | 2019-07-28 22:22:40 +0200 |
commit | 7a30bdd99f37352b188575b27924c407c6ddff9e (patch) | |
tree | 10ea40ab1b5211e75c33eaddb3a6b393ad6ee7ad /Documentation/arm64/hugetlbpage.rst | |
parent | x86/speculation/swapgs: Exclude ATOMs from speculation through SWAPGS (diff) | |
parent | Linux 5.3-rc2 (diff) | |
download | linux-dev-7a30bdd99f37352b188575b27924c407c6ddff9e.tar.xz linux-dev-7a30bdd99f37352b188575b27924c407c6ddff9e.zip |
Merge branch master from git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Pick up the spectre documentation so the Grand Schemozzle can be added.
Diffstat (limited to 'Documentation/arm64/hugetlbpage.rst')
-rw-r--r-- | Documentation/arm64/hugetlbpage.rst | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/Documentation/arm64/hugetlbpage.rst b/Documentation/arm64/hugetlbpage.rst new file mode 100644 index 000000000000..b44f939e5210 --- /dev/null +++ b/Documentation/arm64/hugetlbpage.rst @@ -0,0 +1,41 @@ +==================== +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 + ====== ======== ==== ======== === |