| What: /sys/devices/system/cpu/ |
| Date: pre-git history |
| Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> |
| Description: |
| A collection of both global and individual CPU attributes |
| |
| Individual CPU attributes are contained in subdirectories |
| named by the kernel's logical CPU number, e.g.: |
| |
| /sys/devices/system/cpu/cpu#/ |
| |
| What: /sys/devices/system/cpu/kernel_max |
| /sys/devices/system/cpu/offline |
| /sys/devices/system/cpu/online |
| /sys/devices/system/cpu/possible |
| /sys/devices/system/cpu/present |
| Date: December 2008 |
| Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> |
| Description: CPU topology files that describe kernel limits related to |
| hotplug. Briefly: |
| |
| kernel_max: the maximum cpu index allowed by the kernel |
| configuration. |
| |
| offline: cpus that are not online because they have been |
| HOTPLUGGED off or exceed the limit of cpus allowed by the |
| kernel configuration (kernel_max above). |
| |
| online: cpus that are online and being scheduled. |
| |
| possible: cpus that have been allocated resources and can be |
| brought online if they are present. |
| |
| present: cpus that have been identified as being present in |
| the system. |
| |
| See Documentation/cputopology.txt for more information. |
| |
| |
| What: /sys/devices/system/cpu/probe |
| /sys/devices/system/cpu/release |
| Date: November 2009 |
| Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> |
| Description: Dynamic addition and removal of CPU's. This is not hotplug |
| removal, this is meant complete removal/addition of the CPU |
| from the system. |
| |
| probe: writes to this file will dynamically add a CPU to the |
| system. Information written to the file to add CPU's is |
| architecture specific. |
| |
| release: writes to this file dynamically remove a CPU from |
| the system. Information writtento the file to remove CPU's |
| is architecture specific. |
| |
| What: /sys/devices/system/cpu/cpu#/node |
| Date: October 2009 |
| Contact: Linux memory management mailing list <linux-mm@kvack.org> |
| Description: Discover NUMA node a CPU belongs to |
| |
| When CONFIG_NUMA is enabled, a symbolic link that points |
| to the corresponding NUMA node directory. |
| |
| For example, the following symlink is created for cpu42 |
| in NUMA node 2: |
| |
| /sys/devices/system/cpu/cpu42/node2 -> ../../node/node2 |
| |
| |
| What: /sys/devices/system/cpu/cpu#/topology/core_id |
| /sys/devices/system/cpu/cpu#/topology/core_siblings |
| /sys/devices/system/cpu/cpu#/topology/core_siblings_list |
| /sys/devices/system/cpu/cpu#/topology/physical_package_id |
| /sys/devices/system/cpu/cpu#/topology/thread_siblings |
| /sys/devices/system/cpu/cpu#/topology/thread_siblings_list |
| Date: December 2008 |
| Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> |
| Description: CPU topology files that describe a logical CPU's relationship |
| to other cores and threads in the same physical package. |
| |
| One cpu# directory is created per logical CPU in the system, |
| e.g. /sys/devices/system/cpu/cpu42/. |
| |
| Briefly, the files above are: |
| |
| core_id: the CPU core ID of cpu#. Typically it is the |
| hardware platform's identifier (rather than the kernel's). |
| The actual value is architecture and platform dependent. |
| |
| core_siblings: internal kernel map of cpu#'s hardware threads |
| within the same physical_package_id. |
| |
| core_siblings_list: human-readable list of the logical CPU |
| numbers within the same physical_package_id as cpu#. |
| |
| physical_package_id: physical package id of cpu#. Typically |
| corresponds to a physical socket number, but the actual value |
| is architecture and platform dependent. |
| |
| thread_siblings: internel kernel map of cpu#'s hardware |
| threads within the same core as cpu# |
| |
| thread_siblings_list: human-readable list of cpu#'s hardware |
| threads within the same core as cpu# |
| |
| See Documentation/cputopology.txt for more information. |
| |
| |
| What: /sys/devices/system/cpu/cpuidle/current_driver |
| /sys/devices/system/cpu/cpuidle/current_governer_ro |
| Date: September 2007 |
| Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> |
| Description: Discover cpuidle policy and mechanism |
| |
| Various CPUs today support multiple idle levels that are |
| differentiated by varying exit latencies and power |
| consumption during idle. |
| |
| Idle policy (governor) is differentiated from idle mechanism |
| (driver) |
| |
| current_driver: displays current idle mechanism |
| |
| current_governor_ro: displays current idle policy |
| |
| See files in Documentation/cpuidle/ for more information. |
| |
| |
| What: /sys/devices/system/cpu/cpu#/cpufreq/* |
| Date: pre-git history |
| Contact: linux-pm@vger.kernel.org |
| Description: Discover and change clock speed of CPUs |
| |
| Clock scaling allows you to change the clock speed of the |
| CPUs on the fly. This is a nice method to save battery |
| power, because the lower the clock speed, the less power |
| the CPU consumes. |
| |
| There are many knobs to tweak in this directory. |
| |
| See files in Documentation/cpu-freq/ for more information. |
| |
| In particular, read Documentation/cpu-freq/user-guide.txt |
| to learn how to control the knobs. |
| |
| |
| What: /sys/devices/system/cpu/cpu#/cpufreq/freqdomain_cpus |
| Date: June 2013 |
| Contact: linux-pm@vger.kernel.org |
| Description: Discover CPUs in the same CPU frequency coordination domain |
| |
| freqdomain_cpus is the list of CPUs (online+offline) that share |
| the same clock/freq domain (possibly at the hardware level). |
| That information may be hidden from the cpufreq core and the |
| value of related_cpus may be different from freqdomain_cpus. This |
| attribute is useful for user space DVFS controllers to get better |
| power/performance results for platforms using acpi-cpufreq. |
| |
| This file is only present if the acpi-cpufreq driver is in use. |
| |
| |
| What: /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1} |
| Date: August 2008 |
| KernelVersion: 2.6.27 |
| Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> |
| Description: Disable L3 cache indices |
| |
| These files exist in every CPU's cache/index3 directory. Each |
| cache_disable_{0,1} file corresponds to one disable slot which |
| can be used to disable a cache index. Reading from these files |
| on a processor with this functionality will return the currently |
| disabled index for that node. There is one L3 structure per |
| node, or per internal node on MCM machines. Writing a valid |
| index to one of these files will cause the specificed cache |
| index to be disabled. |
| |
| All AMD processors with L3 caches provide this functionality. |
| For details, see BKDGs at |
| http://developer.amd.com/documentation/guides/Pages/default.aspx |
| |
| |
| What: /sys/devices/system/cpu/cpufreq/boost |
| Date: August 2012 |
| Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> |
| Description: Processor frequency boosting control |
| |
| This switch controls the boost setting for the whole system. |
| Boosting allows the CPU and the firmware to run at a frequency |
| beyound it's nominal limit. |
| More details can be found in Documentation/cpu-freq/boost.txt |
| |
| |
| What: /sys/devices/system/cpu/cpu#/crash_notes |
| /sys/devices/system/cpu/cpu#/crash_notes_size |
| Date: April 2013 |
| Contact: kexec@lists.infradead.org |
| Description: address and size of the percpu note. |
| |
| crash_notes: the physical address of the memory that holds the |
| note of cpu#. |
| |
| crash_notes_size: size of the note of cpu#. |
| |
| |
| What: /sys/devices/system/cpu/intel_pstate/max_perf_pct |
| /sys/devices/system/cpu/intel_pstate/min_perf_pct |
| /sys/devices/system/cpu/intel_pstate/no_turbo |
| Date: February 2013 |
| Contact: linux-pm@vger.kernel.org |
| Description: Parameters for the Intel P-state driver |
| |
| Logic for selecting the current P-state in Intel |
| Sandybridge+ processors. The three knobs control |
| limits for the P-state that will be requested by the |
| driver. |
| |
| max_perf_pct: limits the maximum P state that will be requested by |
| the driver stated as a percentage of the available performance. |
| |
| min_perf_pct: limits the minimum P state that will be requested by |
| the driver stated as a percentage of the available performance. |
| |
| no_turbo: limits the driver to selecting P states below the turbo |
| frequency range. |
| |
| More details can be found in Documentation/cpu-freq/intel-pstate.txt |
| |
| What: /sys/devices/system/cpu/cpu*/cache/index*/<set_of_attributes_mentioned_below> |
| Date: July 2014(documented, existed before August 2008) |
| Contact: Sudeep Holla <sudeep.holla@arm.com> |
| Linux kernel mailing list <linux-kernel@vger.kernel.org> |
| Description: Parameters for the CPU cache attributes |
| |
| allocation_policy: |
| - WriteAllocate: allocate a memory location to a cache line |
| on a cache miss because of a write |
| - ReadAllocate: allocate a memory location to a cache line |
| on a cache miss because of a read |
| - ReadWriteAllocate: both writeallocate and readallocate |
| |
| attributes: LEGACY used only on IA64 and is same as write_policy |
| |
| coherency_line_size: the minimum amount of data in bytes that gets |
| transferred from memory to cache |
| |
| level: the cache hierarcy in the multi-level cache configuration |
| |
| number_of_sets: total number of sets in the cache, a set is a |
| collection of cache lines with the same cache index |
| |
| physical_line_partition: number of physical cache line per cache tag |
| |
| shared_cpu_list: the list of logical cpus sharing the cache |
| |
| shared_cpu_map: logical cpu mask containing the list of cpus sharing |
| the cache |
| |
| size: the total cache size in kB |
| |
| type: |
| - Instruction: cache that only holds instructions |
| - Data: cache that only caches data |
| - Unified: cache that holds both data and instructions |
| |
| ways_of_associativity: degree of freedom in placing a particular block |
| of memory in the cache |
| |
| write_policy: |
| - WriteThrough: data is written to both the cache line |
| and to the block in the lower-level memory |
| - WriteBack: data is written only to the cache line and |
| the modified cache line is written to main |
| memory only when it is replaced |
