| 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/sched_mc_power_savings |
| /sys/devices/system/cpu/sched_smt_power_savings |
| Date: June 2006 |
| Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> |
| Description: Discover and adjust the kernel's multi-core scheduler support. |
| |
| Possible values are: |
| |
| 0 - No power saving load balance (default value) |
| 1 - Fill one thread/core/package first for long running threads |
| 2 - Also bias task wakeups to semi-idle cpu package for power |
| savings |
| |
| sched_mc_power_savings is dependent upon SCHED_MC, which is |
| itself architecture dependent. |
| |
| sched_smt_power_savings is dependent upon SCHED_SMT, which |
| is itself architecture dependent. |
| |
| The two files are independent of each other. It is possible |
| that one file may be present without the other. |
| |
| Introduced by git commit 5c45bf27. |
| |
| |
| 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#/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: cpufreq@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*/cache/index*/cache_disable_X |
| Date: August 2008 |
| KernelVersion: 2.6.27 |
| Contact: mark.langsdorf@amd.com |
| Description: These files exist in every cpu's cache index directories. |
| There are currently 2 cache_disable_# files in each |
| directory. Reading from these files on a supported |
| processor will return that cache disable index value |
| for that processor and node. Writing to one of these |
| files will cause the specificed cache index to be disabled. |
| |
| Currently, only AMD Family 10h Processors support cache index |
| disable, and only for their L3 caches. See the BIOS and |
| Kernel Developer's Guide at |
| http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/31116-Public-GH-BKDG_3.20_2-4-09.pdf |
| for formatting information and other details on the |
| cache index disable. |
| Users: joachim.deguara@amd.com |