CONFIG_SHUFFLE_PAGE_ALLOCATOR: Page allocator randomization

General informations

The Linux kernel configuration item CONFIG_SHUFFLE_PAGE_ALLOCATOR has multiple definitions:

Page allocator randomization found in mm/Kconfig

The configuration item CONFIG_SHUFFLE_PAGE_ALLOCATOR:

• prompt: Page allocator randomization
• type: bool
• depends on: (none)
• defined in mm/Kconfig
• found in Linux kernels: 5.19, 6.0–6.12, 6.13-rc+HEAD

Help text

Randomization of the page allocator improves the average utilization of a direct-mapped memory-side-cache. See section 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 6.2a specification for an example of how a platform advertises the presence of a memory-side-cache. There are also incidental security benefits as it reduces the predictability of page allocations to compliment SLAB_FREELIST_RANDOM, but the default granularity of shuffling on the MAX_PAGE_ORDER i.e, 10th order of pages is selected based on cache utilization benefits on x86.

While the randomization improves cache utilization it may negatively impact workloads on platforms without a cache. For this reason, by default, the randomization is not enabled even if SHUFFLE_PAGE_ALLOCATOR=y. The randomization may be force enabled with the 'page_alloc.shuffle' kernel command line parameter.

Say Y if unsure.

Page allocator randomization found in init/Kconfig

The configuration item CONFIG_SHUFFLE_PAGE_ALLOCATOR:

• prompt: Page allocator randomization
• type: bool
• depends on: (none)
• defined in init/Kconfig
• found in Linux kernels: 5.2–5.18, 5.18+HEAD

Help text

Randomization of the page allocator improves the average utilization of a direct-mapped memory-side-cache. See section 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 6.2a specification for an example of how a platform advertises the presence of a memory-side-cache. There are also incidental security benefits as it reduces the predictability of page allocations to compliment SLAB_FREELIST_RANDOM, but the default granularity of shuffling on the "MAX_ORDER - 1" i.e, 10th order of pages is selected based on cache utilization benefits on x86.

While the randomization improves cache utilization it may negatively impact workloads on platforms without a cache. For this reason, by default, the randomization is enabled only after runtime detection of a direct-mapped memory-side-cache. Otherwise, the randomization may be force enabled with the 'page_alloc.shuffle' kernel command line parameter.

Say Y if unsure.

Hardware

LKDDb

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• (none)

Sources

This page is automaticly generated with free (libre, open) software lkddb(see lkddb-sources).

The data is retrived from:

• Linux kernel
• Linux Kernel Driver DataBase (LKDDb)

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