CONFIG_UACCESS_WITH_MEMCPY: Use kernel mem{cpy,set}() for {copy_to,clear}_user()

General informations

The Linux kernel configuration item CONFIG_UACCESS_WITH_MEMCPY has multiple definitions:

Use kernel mem{cpy,set}() for {copy_to,clear}_user() found in arch/arm/Kconfig

The configuration item CONFIG_UACCESS_WITH_MEMCPY:

• prompt: Use kernel mem{cpy,set}() for {copy_to,clear}_user()
• type: bool
• depends on: ( CONFIG_MMU ) && ( CONFIG_CPU_FEROCEON )
• defined in arch/arm/Kconfig
• found in Linux kernels: 3.7–3.19, 4.0–4.20, 5.0–5.19, 6.0–6.12, 6.13-rc+HEAD

Help text

Implement faster copy_to_user and clear_user methods for CPU cores where a 8-word STM instruction give significantly higher memory write throughput than a sequence of individual 32bit stores.

A possible side effect is a slight increase in scheduling latency between threads sharing the same address space if they invoke such copy operations with large buffers.

However, if the CPU data cache is using a write-allocate mode, this option is unlikely to provide any performance gain.

Use kernel mem{cpy,set}() for {copy_to,clear}_user() (EXPERIMENTAL) found in arch/arm/Kconfig

The configuration item CONFIG_UACCESS_WITH_MEMCPY:

• prompt: Use kernel mem{cpy,set}() for {copy_to,clear}_user() (EXPERIMENTAL)
• type: bool
• depends on: ( CONFIG_MMU && CONFIG_EXPERIMENTAL ) && ( CONFIG_CPU_FEROCEON )
• defined in arch/arm/Kconfig
• found in Linux kernels: 2.6.31–2.6.39, 3.0–3.6

Help text

Implement faster copy_to_user and clear_user methods for CPU cores where a 8-word STM instruction give significantly higher memory write throughput than a sequence of individual 32bit stores.

A possible side effect is a slight increase in scheduling latency between threads sharing the same address space if they invoke such copy operations with large buffers.

However, if the CPU data cache is using a write-allocate mode, this option is unlikely to provide any performance gain.

Hardware

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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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