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This patch adds initial support for providing processor cache information to userspace through sysfs interface. This is based on already existing implementations(x86, ia64, s390 and powerpc) and hence the interface is intended to be fully compatible. The main purpose of this generic support is to avoid further code duplication to support new architectures and also to unify all the existing different implementations. This implementation maintains the hierarchy of cache objects which reflects the system's cache topology. Cache devices are instantiated as needed as CPUs come online. The cache information is replicated per-cpu even if they are shared. A per-cpu array of cache information maintained is used mainly for sysfs-related book keeping. It also implements the shared_cpu_map attribute, which is essential for enabling both kernel and user-space to discover the system's overall cache topology. This patch also add the missing ABI documentation for the cacheinfo sysfs interface already, which is well defined and widely used. Signed-off-by: Sudeep Holla <sudeep.holla@arm.com> Reviewed-by: Stephen Boyd <sboyd@codeaurora.org> Tested-by: Stephen Boyd <sboyd@codeaurora.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: linux-api@vger.kernel.org Cc: linux390@de.ibm.com Cc: linux-arm-kernel@lists.infradead.org Cc: linux-ia64@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: linux-s390@vger.kernel.org Cc: x86@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
274 lines
9.6 KiB
Plaintext
274 lines
9.6 KiB
Plaintext
What: /sys/devices/system/cpu/
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Date: pre-git history
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Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
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Description:
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A collection of both global and individual CPU attributes
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Individual CPU attributes are contained in subdirectories
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named by the kernel's logical CPU number, e.g.:
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/sys/devices/system/cpu/cpu#/
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What: /sys/devices/system/cpu/kernel_max
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/sys/devices/system/cpu/offline
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/sys/devices/system/cpu/online
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/sys/devices/system/cpu/possible
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/sys/devices/system/cpu/present
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Date: December 2008
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Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
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Description: CPU topology files that describe kernel limits related to
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hotplug. Briefly:
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kernel_max: the maximum cpu index allowed by the kernel
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configuration.
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offline: cpus that are not online because they have been
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HOTPLUGGED off or exceed the limit of cpus allowed by the
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kernel configuration (kernel_max above).
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online: cpus that are online and being scheduled.
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possible: cpus that have been allocated resources and can be
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brought online if they are present.
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present: cpus that have been identified as being present in
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the system.
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See Documentation/cputopology.txt for more information.
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What: /sys/devices/system/cpu/probe
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/sys/devices/system/cpu/release
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Date: November 2009
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Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
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Description: Dynamic addition and removal of CPU's. This is not hotplug
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removal, this is meant complete removal/addition of the CPU
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from the system.
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probe: writes to this file will dynamically add a CPU to the
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system. Information written to the file to add CPU's is
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architecture specific.
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release: writes to this file dynamically remove a CPU from
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the system. Information writtento the file to remove CPU's
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is architecture specific.
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What: /sys/devices/system/cpu/cpu#/node
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Date: October 2009
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Contact: Linux memory management mailing list <linux-mm@kvack.org>
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Description: Discover NUMA node a CPU belongs to
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When CONFIG_NUMA is enabled, a symbolic link that points
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to the corresponding NUMA node directory.
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For example, the following symlink is created for cpu42
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in NUMA node 2:
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/sys/devices/system/cpu/cpu42/node2 -> ../../node/node2
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What: /sys/devices/system/cpu/cpu#/topology/core_id
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/sys/devices/system/cpu/cpu#/topology/core_siblings
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/sys/devices/system/cpu/cpu#/topology/core_siblings_list
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/sys/devices/system/cpu/cpu#/topology/physical_package_id
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/sys/devices/system/cpu/cpu#/topology/thread_siblings
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/sys/devices/system/cpu/cpu#/topology/thread_siblings_list
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Date: December 2008
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Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
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Description: CPU topology files that describe a logical CPU's relationship
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to other cores and threads in the same physical package.
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One cpu# directory is created per logical CPU in the system,
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e.g. /sys/devices/system/cpu/cpu42/.
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Briefly, the files above are:
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core_id: the CPU core ID of cpu#. Typically it is the
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hardware platform's identifier (rather than the kernel's).
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The actual value is architecture and platform dependent.
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core_siblings: internal kernel map of cpu#'s hardware threads
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within the same physical_package_id.
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core_siblings_list: human-readable list of the logical CPU
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numbers within the same physical_package_id as cpu#.
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physical_package_id: physical package id of cpu#. Typically
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corresponds to a physical socket number, but the actual value
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is architecture and platform dependent.
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thread_siblings: internel kernel map of cpu#'s hardware
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threads within the same core as cpu#
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thread_siblings_list: human-readable list of cpu#'s hardware
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threads within the same core as cpu#
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See Documentation/cputopology.txt for more information.
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What: /sys/devices/system/cpu/cpuidle/current_driver
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/sys/devices/system/cpu/cpuidle/current_governer_ro
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Date: September 2007
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Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
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Description: Discover cpuidle policy and mechanism
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Various CPUs today support multiple idle levels that are
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differentiated by varying exit latencies and power
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consumption during idle.
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Idle policy (governor) is differentiated from idle mechanism
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(driver)
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current_driver: displays current idle mechanism
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current_governor_ro: displays current idle policy
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See files in Documentation/cpuidle/ for more information.
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What: /sys/devices/system/cpu/cpu#/cpufreq/*
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Date: pre-git history
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Contact: linux-pm@vger.kernel.org
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Description: Discover and change clock speed of CPUs
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Clock scaling allows you to change the clock speed of the
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CPUs on the fly. This is a nice method to save battery
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power, because the lower the clock speed, the less power
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the CPU consumes.
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There are many knobs to tweak in this directory.
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See files in Documentation/cpu-freq/ for more information.
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In particular, read Documentation/cpu-freq/user-guide.txt
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to learn how to control the knobs.
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What: /sys/devices/system/cpu/cpu#/cpufreq/freqdomain_cpus
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Date: June 2013
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Contact: linux-pm@vger.kernel.org
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Description: Discover CPUs in the same CPU frequency coordination domain
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freqdomain_cpus is the list of CPUs (online+offline) that share
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the same clock/freq domain (possibly at the hardware level).
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That information may be hidden from the cpufreq core and the
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value of related_cpus may be different from freqdomain_cpus. This
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attribute is useful for user space DVFS controllers to get better
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power/performance results for platforms using acpi-cpufreq.
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This file is only present if the acpi-cpufreq driver is in use.
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What: /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1}
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Date: August 2008
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KernelVersion: 2.6.27
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Contact: discuss@x86-64.org
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Description: Disable L3 cache indices
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These files exist in every CPU's cache/index3 directory. Each
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cache_disable_{0,1} file corresponds to one disable slot which
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can be used to disable a cache index. Reading from these files
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on a processor with this functionality will return the currently
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disabled index for that node. There is one L3 structure per
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node, or per internal node on MCM machines. Writing a valid
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index to one of these files will cause the specificed cache
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index to be disabled.
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All AMD processors with L3 caches provide this functionality.
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For details, see BKDGs at
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http://developer.amd.com/documentation/guides/Pages/default.aspx
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What: /sys/devices/system/cpu/cpufreq/boost
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Date: August 2012
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Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
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Description: Processor frequency boosting control
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This switch controls the boost setting for the whole system.
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Boosting allows the CPU and the firmware to run at a frequency
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beyound it's nominal limit.
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More details can be found in Documentation/cpu-freq/boost.txt
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What: /sys/devices/system/cpu/cpu#/crash_notes
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/sys/devices/system/cpu/cpu#/crash_notes_size
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Date: April 2013
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Contact: kexec@lists.infradead.org
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Description: address and size of the percpu note.
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crash_notes: the physical address of the memory that holds the
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note of cpu#.
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crash_notes_size: size of the note of cpu#.
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What: /sys/devices/system/cpu/intel_pstate/max_perf_pct
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/sys/devices/system/cpu/intel_pstate/min_perf_pct
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/sys/devices/system/cpu/intel_pstate/no_turbo
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Date: February 2013
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Contact: linux-pm@vger.kernel.org
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Description: Parameters for the Intel P-state driver
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Logic for selecting the current P-state in Intel
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Sandybridge+ processors. The three knobs control
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limits for the P-state that will be requested by the
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driver.
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max_perf_pct: limits the maximum P state that will be requested by
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the driver stated as a percentage of the available performance.
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min_perf_pct: limits the minimum P state that will be requested by
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the driver stated as a percentage of the available performance.
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no_turbo: limits the driver to selecting P states below the turbo
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frequency range.
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More details can be found in Documentation/cpu-freq/intel-pstate.txt
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What: /sys/devices/system/cpu/cpu*/cache/index*/<set_of_attributes_mentioned_below>
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Date: July 2014(documented, existed before August 2008)
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Contact: Sudeep Holla <sudeep.holla@arm.com>
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Linux kernel mailing list <linux-kernel@vger.kernel.org>
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Description: Parameters for the CPU cache attributes
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allocation_policy:
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- WriteAllocate: allocate a memory location to a cache line
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on a cache miss because of a write
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- ReadAllocate: allocate a memory location to a cache line
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on a cache miss because of a read
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- ReadWriteAllocate: both writeallocate and readallocate
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attributes: LEGACY used only on IA64 and is same as write_policy
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coherency_line_size: the minimum amount of data in bytes that gets
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transferred from memory to cache
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level: the cache hierarcy in the multi-level cache configuration
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number_of_sets: total number of sets in the cache, a set is a
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collection of cache lines with the same cache index
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physical_line_partition: number of physical cache line per cache tag
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shared_cpu_list: the list of logical cpus sharing the cache
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shared_cpu_map: logical cpu mask containing the list of cpus sharing
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the cache
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size: the total cache size in kB
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type:
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- Instruction: cache that only holds instructions
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- Data: cache that only caches data
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- Unified: cache that holds both data and instructions
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ways_of_associativity: degree of freedom in placing a particular block
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of memory in the cache
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write_policy:
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- WriteThrough: data is written to both the cache line
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and to the block in the lower-level memory
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- WriteBack: data is written only to the cache line and
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the modified cache line is written to main
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memory only when it is replaced
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