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Documentation: x86: convert topology.txt to reST
This converts the plain text documentation to reStructuredText format and add it to Sphinx TOC tree. No essential content change. Signed-off-by: Changbin Du <changbin.du@gmail.com> Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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Changbin Du
Jonathan Corbet
parent
f1f238a9f1
commit
848942cb2e
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@ -9,3 +9,4 @@ x86-specific Documentation
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:numbered:
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boot
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topology
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@ -1,3 +1,6 @@
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.. SPDX-License-Identifier: GPL-2.0
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============
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x86 Topology
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============
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@ -33,14 +36,14 @@ The topology of a system is described in the units of:
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- cores
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- threads
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* Package:
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Package
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=======
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Packages contain a number of cores plus shared resources, e.g. DRAM
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controller, shared caches etc.
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Packages contain a number of cores plus shared resources, e.g. DRAM
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controller, shared caches etc.
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AMD nomenclature for package is 'Node'.
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AMD nomenclature for package is 'Node'.
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Package-related topology information in the kernel:
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Package-related topology information in the kernel:
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- cpuinfo_x86.x86_max_cores:
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@ -66,40 +69,41 @@ The topology of a system is described in the units of:
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- cpu_llc_id:
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A per-CPU variable containing:
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- On Intel, the first APIC ID of the list of CPUs sharing the Last Level
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Cache
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- On AMD, the Node ID or Core Complex ID containing the Last Level
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Cache. In general, it is a number identifying an LLC uniquely on the
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system.
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- On Intel, the first APIC ID of the list of CPUs sharing the Last Level
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Cache
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* Cores:
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- On AMD, the Node ID or Core Complex ID containing the Last Level
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Cache. In general, it is a number identifying an LLC uniquely on the
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system.
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A core consists of 1 or more threads. It does not matter whether the threads
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are SMT- or CMT-type threads.
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Cores
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=====
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A core consists of 1 or more threads. It does not matter whether the threads
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are SMT- or CMT-type threads.
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AMDs nomenclature for a CMT core is "Compute Unit". The kernel always uses
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"core".
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AMDs nomenclature for a CMT core is "Compute Unit". The kernel always uses
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"core".
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Core-related topology information in the kernel:
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Core-related topology information in the kernel:
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- smp_num_siblings:
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The number of threads in a core. The number of threads in a package can be
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calculated by:
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calculated by::
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threads_per_package = cpuinfo_x86.x86_max_cores * smp_num_siblings
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* Threads:
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Threads
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=======
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A thread is a single scheduling unit. It's the equivalent to a logical Linux
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CPU.
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A thread is a single scheduling unit. It's the equivalent to a logical Linux
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CPU.
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AMDs nomenclature for CMT threads is "Compute Unit Core". The kernel always
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uses "thread".
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AMDs nomenclature for CMT threads is "Compute Unit Core". The kernel always
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uses "thread".
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Thread-related topology information in the kernel:
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Thread-related topology information in the kernel:
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- topology_core_cpumask():
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@ -113,15 +117,15 @@ The topology of a system is described in the units of:
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The cpumask contains all online threads in the core to which a thread
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belongs.
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- topology_logical_package_id():
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- topology_logical_package_id():
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The logical package ID to which a thread belongs.
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- topology_physical_package_id():
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- topology_physical_package_id():
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The physical package ID to which a thread belongs.
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- topology_core_id();
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- topology_core_id();
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The ID of the core to which a thread belongs. It is also printed in /proc/cpuinfo
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"core_id."
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@ -129,41 +133,41 @@ The topology of a system is described in the units of:
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System topology examples
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========================
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Note:
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.. note::
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The alternative Linux CPU enumeration depends on how the BIOS enumerates the
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threads. Many BIOSes enumerate all threads 0 first and then all threads 1.
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That has the "advantage" that the logical Linux CPU numbers of threads 0 stay
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the same whether threads are enabled or not. That's merely an implementation
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detail and has no practical impact.
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The alternative Linux CPU enumeration depends on how the BIOS enumerates the
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threads. Many BIOSes enumerate all threads 0 first and then all threads 1.
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That has the "advantage" that the logical Linux CPU numbers of threads 0 stay
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the same whether threads are enabled or not. That's merely an implementation
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detail and has no practical impact.
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1) Single Package, Single Core
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1) Single Package, Single Core::
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[package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
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2) Single Package, Dual Core
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a) One thread per core
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a) One thread per core::
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[package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
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-> [core 1] -> [thread 0] -> Linux CPU 1
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b) Two threads per core
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b) Two threads per core::
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[package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
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-> [thread 1] -> Linux CPU 1
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-> [core 1] -> [thread 0] -> Linux CPU 2
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-> [thread 1] -> Linux CPU 3
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Alternative enumeration:
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Alternative enumeration::
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[package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
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-> [thread 1] -> Linux CPU 2
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-> [core 1] -> [thread 0] -> Linux CPU 1
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-> [thread 1] -> Linux CPU 3
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AMD nomenclature for CMT systems:
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AMD nomenclature for CMT systems::
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[node 0] -> [Compute Unit 0] -> [Compute Unit Core 0] -> Linux CPU 0
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-> [Compute Unit Core 1] -> Linux CPU 1
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@ -172,7 +176,7 @@ detail and has no practical impact.
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4) Dual Package, Dual Core
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a) One thread per core
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a) One thread per core::
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[package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
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-> [core 1] -> [thread 0] -> Linux CPU 1
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@ -180,7 +184,7 @@ detail and has no practical impact.
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[package 1] -> [core 0] -> [thread 0] -> Linux CPU 2
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-> [core 1] -> [thread 0] -> Linux CPU 3
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b) Two threads per core
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b) Two threads per core::
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[package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
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-> [thread 1] -> Linux CPU 1
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@ -192,7 +196,7 @@ detail and has no practical impact.
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-> [core 1] -> [thread 0] -> Linux CPU 6
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-> [thread 1] -> Linux CPU 7
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Alternative enumeration:
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Alternative enumeration::
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[package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
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-> [thread 1] -> Linux CPU 4
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@ -204,7 +208,7 @@ detail and has no practical impact.
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-> [core 1] -> [thread 0] -> Linux CPU 3
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-> [thread 1] -> Linux CPU 7
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AMD nomenclature for CMT systems:
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AMD nomenclature for CMT systems::
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[node 0] -> [Compute Unit 0] -> [Compute Unit Core 0] -> Linux CPU 0
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-> [Compute Unit Core 1] -> Linux CPU 1
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