This describes the sysfs interface implemented by the hardware prefetch control driver. Signed-off-by: Kohei Tarumizu <tarumizu.kohei@xxxxxxxxxxx> --- .../ABI/testing/sysfs-devices-system-cpu | 98 +++++++++++++++++++ 1 file changed, 98 insertions(+) diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu index 2ad01cad7f1c..0da4c1bac51e 100644 --- a/Documentation/ABI/testing/sysfs-devices-system-cpu +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu @@ -688,3 +688,101 @@ Description: (RO) the list of CPUs that are isolated and don't participate in load balancing. These CPUs are set by boot parameter "isolcpus=". + +What: /sys/devices/system/cpu/cpu*/cache/index*/prefetch_control/hardware_prefetcher_enable + /sys/devices/system/cpu/cpu*/cache/index*/prefetch_control/ip_prefetcher_enable + /sys/devices/system/cpu/cpu*/cache/index*/prefetch_control/adjacent_cache_line_prefetcher_enable +Date: March 2022 +Contact: Linux kernel mailing list <linux-kernel@xxxxxxxxxxxxxxx> +Description: Parameters for some Intel CPU's hardware prefetch control + + This sysfs interface provides Hardware Prefetch control + attribute for some Intel processors. Attributes are only + present if the particular cache implements the relevant + prefetcher controls. + + *_prefetcher_enable: + (RW) control this prefetcher's enablement state. + Read returns current status: + 0: this prefetcher is disabled + 1: this prefetcher is enabled + + - Attribute mapping + + Some Intel processors have MSR 0x1a4. This register has several + specifications depending on the model. This interface provides + a one-to-one attribute file to control all the tunable + parameters the CPU provides of the following. + + - "* Hardware Prefetcher Disable (R/W)" + corresponds to the "hardware_prefetcher_enable" + + - "* Adjacent Cache Line Prefetcher Disable (R/W)" + corresponds to the "adjacent_cache_line_prefetcher_enable" + + - "* IP Prefetcher Disable (R/W)" + corresponds to the "ip_prefetcher_enable" + +What: /sys/devices/system/cpu/cpu*/cache/index*/prefetch_control/stream_detect_prefetcher_enable + /sys/devices/system/cpu/cpu*/cache/index*/prefetch_control/stream_detect_prefetcher_strength + /sys/devices/system/cpu/cpu*/cache/index*/prefetch_control/stream_detect_prefetcher_strength_available + /sys/devices/system/cpu/cpu*/cache/index*/prefetch_control/stream_detect_prefetcher_dist +Date: March 2022 +Contact: Linux kernel mailing list <linux-kernel@xxxxxxxxxxxxxxx> +Description: Parameters for A64FX's hardware prefetch control + + This sysfs interface provides Hardware Prefetch control + attribute for the processor A64FX. Attributes are only + present if the particular cache implements the relevant + prefetcher controls. + + stream_detect_prefetcher_enable: + (RW) control the prefetcher's enablement state. + Read returns current status: + 0: this prefetcher is disabled + 1: this prefetcher is enabled + + stream_detect_prefetcher_strength: + (RW) control the prefetcher operation's strongness state. + Read returns current status: + weak: prefetch operation is weak + strong: prefetch operation is strong + + Strong prefetch operation is surely executed, if there is + no corresponding data in cache. + Weak prefetch operation allows the hardware not to execute + operation depending on hardware state. + + + stream_detect_prefetcher_strength_available: + (RO) displays a space separated list of available strongness + state. + + stream_detect_prefetcher_dist: + (RW) control the prefetcher distance value. + Read return current prefetcher distance value in bytes + or the string "auto". + + Write either a value in byte or the string "auto" to this + parameter. If you write a value less than multiples of a + specific value, it is rounded up. + + The string "auto" have a special meaning. This means that + instead of setting dist to a user-specified value, it + operates using hardware-specific values. + + - Attribute mapping + + The processor A64FX has register IMP_PF_STREAM_DETECT_CTRL_EL0 + for Hardware Prefetch Control. This attribute maps each + specification to the following. + + - "L*PF_DIS": enablement of hardware prefetcher + corresponds to the "stream_detect_prefetcher_enable" + + - "L*W": strongness of hardware prefetcher + corresponds to "stream_detect_prefetcher_strength" + and "stream_detect_prefetcher_strength_available" + + - "L*_DIST": distance of hardware prefetcher + corresponds to the "stream_detect_prefetcher_dist" -- 2.27.0
