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

General informations

The Linux kernel configuration item CONFIG_UACCESS_WITH_MEMCPY has multiple definitions:

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

The configuration item CONFIG_UACCESS_WITH_MEMCPY:

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() found in arch/arm/Kconfig

The configuration item CONFIG_UACCESS_WITH_MEMCPY:

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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