Messages in this thread Patch in this message | | | From | Kohei Tarumizu <> | Subject | [PATCH v2 8/8] docs: ABI: Add sysfs documentation interface of hardware prefetch control driver | Date | Fri, 11 Mar 2022 19:19:40 +0900 |
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This describes the sysfs interface implemented on the hardware prefetch control driver.
Signed-off-by: Kohei Tarumizu <tarumizu.kohei@fujitsu.com> --- .../ABI/testing/sysfs-devices-system-cpu | 89 +++++++++++++++++++ 1 file changed, 89 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu index 61f5676a7429..c1f6aa1322da 100644 --- a/Documentation/ABI/testing/sysfs-devices-system-cpu +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu @@ -681,3 +681,92 @@ 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[0,2]/prefetch_control + /sys/devices/system/cpu/cpu*/cache/index[0,2]/prefetch_control/hardware_prefetcher_enable + /sys/devices/system/cpu/cpu*/cache/index[0,2]/prefetch_control/ip_prefetcher_enable + /sys/devices/system/cpu/cpu*/cache/index[0,2]/prefetch_control/adjacent_cache_line_prefetcher_enable + /sys/devices/system/cpu/cpu*/cache/index[0,2]/prefetch_control/stream_detect_prefetcher_enable + /sys/devices/system/cpu/cpu*/cache/index[0,2]/prefetch_control/stream_detect_prefetcher_strong + /sys/devices/system/cpu/cpu*/cache/index[0,2]/prefetch_control/stream_detect_prefetcher_dist +Date: March 2022 +Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> +Description: Parameters for CPU's hardware prefetch control + + This sysfs interface provides Hardware Prefetch control + attribute file by using implementation defined registers. + These files exists in every CPU's cache/index[0,2] directory, + and these affect the cache level of the parent index directory. + Each attribute file exists depending on kind of processor and + cache level. + + *_prefetcher_enable: + (RW) control this prefetcher's enablement state. + Read returns current status: + 0: this prefetcher is disabled + 1: this prefetcher is enabled + + stream_detect_prefetcher_strong: + (RW) control prefetcher operation's strongness state. + 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. + + Read returns current status: + 0: prefetch operation is weak + 1: prefetch operation is strong + + 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 value 0 and the string "auto" are the same and have + a special meaning. This means that instead of setting + dist to a user-specified value, it operates using + hardware-specific values. + + - Supported processors + + This sysfs interface is available on several processors, x86 + and ARM64. Currently, the following processors are supported: + + - x86 processor + - INTEL_FAM6_BROADWELL_X + + - ARM64 processor + - FUJITSU_CPU_PART_A64FX + + - 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" + + 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 the "stream_detect_prefetcher_strong" + + - "L*_DIST": distance of hardware prefetcher + corresponds to the "stream_detect_prefetcher_dist" -- 2.27.0
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