[PATCH v4 39/63] Documentation: x86: convert topology.txt to reST

Changbin Du
2019-04-23T16:29:08Z

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>
---
Documentation/x86/index.rst | 1 +
Documentation/x86/topology.rst | 228 +++++++++++++++++++++++++++++++++
Documentation/x86/topology.txt | 217 -------------------------------
3 files changed, 229 insertions(+), 217 deletions(-)
create mode 100644 Documentation/x86/topology.rst
delete mode 100644 Documentation/x86/topology.txt

diff --git a/Documentation/x86/index.rst b/Documentation/x86/index.rst
index 8f08caf4fbbb..2033791e53bc 100644
--- a/Documentation/x86/index.rst
+++ b/Documentation/x86/index.rst
@@ -9,3 +9,4 @@ Linux x86 Support
:numbered:

boot
+ topology
diff --git a/Documentation/x86/topology.rst b/Documentation/x86/topology.rst
new file mode 100644
index 000000000000..1df5f56f4882
--- /dev/null
+++ b/Documentation/x86/topology.rst
@@ -0,0 +1,228 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+============
+x86 Topology
+============
+
+This documents and clarifies the main aspects of x86 topology modelling and
+representation in the kernel. Update/change when doing changes to the
+respective code.
+
+The architecture-agnostic topology definitions are in
+Documentation/cputopology.txt. This file holds x86-specific
+differences/specialities which must not necessarily apply to the generic
+definitions. Thus, the way to read up on Linux topology on x86 is to start
+with the generic one and look at this one in parallel for the x86 specifics.
+
+Needless to say, code should use the generic functions - this file is *only*
+here to *document* the inner workings of x86 topology.
+
+Started by Thomas Gleixner <tglx@linutronix.de> and Borislav Petkov <bp@alien8.de>.
+
+The main aim of the topology facilities is to present adequate interfaces to
+code which needs to know/query/use the structure of the running system wrt
+threads, cores, packages, etc.
+
+The kernel does not care about the concept of physical sockets because a
+socket has no relevance to software. It's an electromechanical component. In
+the past a socket always contained a single package (see below), but with the
+advent of Multi Chip Modules (MCM) a socket can hold more than one package. So
+there might be still references to sockets in the code, but they are of
+historical nature and should be cleaned up.
+
+The topology of a system is described in the units of:
+
+ - packages
+ - cores
+ - threads
+
+Package
+=======
+
+Packages contain a number of cores plus shared resources, e.g. DRAM
+controller, shared caches etc.
+
+AMD nomenclature for package is 'Node'.
+
+Package-related topology information in the kernel:
+
+ - cpuinfo_x86.x86_max_cores:
+
+ The number of cores in a package. This information is retrieved via CPUID.
+
+ - cpuinfo_x86.phys_proc_id:
+
+ The physical ID of the package. This information is retrieved via CPUID
+ and deduced from the APIC IDs of the cores in the package.
+
+ - cpuinfo_x86.logical_id:
+
+ The logical ID of the package. As we do not trust BIOSes to enumerate the
+ packages in a consistent way, we introduced the concept of logical package
+ ID so we can sanely calculate the number of maximum possible packages in
+ the system and have the packages enumerated linearly.
+
+ - topology_max_packages():
+
+ The maximum possible number of packages in the system. Helpful for per
+ package facilities to preallocate per package information.
+
+ - cpu_llc_id:
+
+ A per-CPU variable containing:
+
+ - On Intel, the first APIC ID of the list of CPUs sharing the Last Level
+ Cache.
+
+ - On AMD, the Node ID or Core Complex ID containing the Last Level
+ Cache. In general, it is a number identifying an LLC uniquely on the
+ system.
+
+Cores
+=====
+
+A core consists of 1 or more threads. It does not matter whether the threads
+are SMT- or CMT-type threads.
+
+AMDs nomenclature for a CMT core is "Compute Unit". The kernel always uses
+"core".
+
+Core-related topology information in the kernel:
+
+ - smp_num_siblings:
+
+ The number of threads in a core. The number of threads in a package can be
+ calculated by::
+
+ threads_per_package = cpuinfo_x86.x86_max_cores * smp_num_siblings
+
+
+Threads
+=======
+
+A thread is a single scheduling unit. It's the equivalent to a logical Linux
+CPU.
+
+AMDs nomenclature for CMT threads is "Compute Unit Core". The kernel always
+uses "thread".
+
+Thread-related topology information in the kernel:
+
+ - topology_core_cpumask():
+
+ The cpumask contains all online threads in the package to which a thread
+ belongs.
+
+ The number of online threads is also printed in /proc/cpuinfo "siblings."
+
+ - topology_sibling_cpumask():
+
+ The cpumask contains all online threads in the core to which a thread
+ belongs.
+
+ - topology_logical_package_id():
+
+ The logical package ID to which a thread belongs.
+
+ - topology_physical_package_id():
+
+ The physical package ID to which a thread belongs.
+
+ - topology_core_id();
+
+ The ID of the core to which a thread belongs. It is also printed in /proc/cpuinfo
+ "core_id."
+
+
+
+System topology examples
+========================
+
+.. note:: The alternative Linux CPU enumeration depends on how the BIOS
+ enumerates the threads. Many BIOSes enumerate all threads 0 first and
+ then all threads 1. That has the "advantage" that the logical Linux CPU
+ numbers of threads 0 stay the same whether threads are enabled or not.
+ That's merely an implementation detail and has no practical impact.
+
+1) Single Package, Single Core
+::
+
+ [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+
+2) Single Package, Dual Core
+
+ a) One thread per core
+ ::
+
+ [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+ -> [core 1] -> [thread 0] -> Linux CPU 1
+
+ b) Two threads per core
+ ::
+
+ [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+ -> [thread 1] -> Linux CPU 1
+ -> [core 1] -> [thread 0] -> Linux CPU 2
+ -> [thread 1] -> Linux CPU 3
+
+ Alternative enumeration::
+
+ [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+ -> [thread 1] -> Linux CPU 2
+ -> [core 1] -> [thread 0] -> Linux CPU 1
+ -> [thread 1] -> Linux CPU 3
+
+ AMD nomenclature for CMT systems::
+
+ [node 0] -> [Compute Unit 0] -> [Compute Unit Core 0] -> Linux CPU 0
+ -> [Compute Unit Core 1] -> Linux CPU 1
+ -> [Compute Unit 1] -> [Compute Unit Core 0] -> Linux CPU 2
+ -> [Compute Unit Core 1] -> Linux CPU 3
+
+4) Dual Package, Dual Core
+
+ a) One thread per core
+ ::
+
+ [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+ -> [core 1] -> [thread 0] -> Linux CPU 1
+
+ [package 1] -> [core 0] -> [thread 0] -> Linux CPU 2
+ -> [core 1] -> [thread 0] -> Linux CPU 3
+
+ b) Two threads per core
+ ::
+
+ [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+ -> [thread 1] -> Linux CPU 1
+ -> [core 1] -> [thread 0] -> Linux CPU 2
+ -> [thread 1] -> Linux CPU 3
+
+ [package 1] -> [core 0] -> [thread 0] -> Linux CPU 4
+ -> [thread 1] -> Linux CPU 5
+ -> [core 1] -> [thread 0] -> Linux CPU 6
+ -> [thread 1] -> Linux CPU 7
+
+ Alternative enumeration::
+
+ [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
+ -> [thread 1] -> Linux CPU 4
+ -> [core 1] -> [thread 0] -> Linux CPU 1
+ -> [thread 1] -> Linux CPU 5
+
+ [package 1] -> [core 0] -> [thread 0] -> Linux CPU 2
+ -> [thread 1] -> Linux CPU 6
+ -> [core 1] -> [thread 0] -> Linux CPU 3
+ -> [thread 1] -> Linux CPU 7
+
+ AMD nomenclature for CMT systems::
+
+ [node 0] -> [Compute Unit 0] -> [Compute Unit Core 0] -> Linux CPU 0
+ -> [Compute Unit Core 1] -> Linux CPU 1
+ -> [Compute Unit 1] -> [Compute Unit Core 0] -> Linux CPU 2
+ -> [Compute Unit Core 1] -> Linux CPU 3
+
+ [node 1] -> [Compute Unit 0] -> [Compute Unit Core 0] -> Linux CPU 4
+ -> [Compute Unit Core 1] -> Linux CPU 5
+ -> [Compute Unit 1] -> [Compute Unit Core 0] -> Linux CPU 6
+ -> [Compute Unit Core 1] -> Linux CPU 7
diff --git a/Documentation/x86/topology.txt b/Documentation/x86/topology.txt
deleted file mode 100644
index 2953e3ec9a02..000000000000
--- a/Documentation/x86/topology.txt
+++ /dev/null
@@ -1,217 +0,0 @@
-x86 Topology
-============
-
-This documents and clarifies the main aspects of x86 topology modelling and
-representation in the kernel. Update/change when doing changes to the
-respective code.
-
-The architecture-agnostic topology definitions are in
-Documentation/cputopology.txt. This file holds x86-specific
-differences/specialities which must not necessarily apply to the generic
-definitions. Thus, the way to read up on Linux topology on x86 is to start
-with the generic one and look at this one in parallel for the x86 specifics.
-
-Needless to say, code should use the generic functions - this file is *only*
-here to *document* the inner workings of x86 topology.
-
-Started by Thomas Gleixner <tglx@linutronix.de> and Borislav Petkov <bp@alien8.de>.
-
-The main aim of the topology facilities is to present adequate interfaces to
-code which needs to know/query/use the structure of the running system wrt
-threads, cores, packages, etc.
-
-The kernel does not care about the concept of physical sockets because a
-socket has no relevance to software. It's an electromechanical component. In
-the past a socket always contained a single package (see below), but with the
-advent of Multi Chip Modules (MCM) a socket can hold more than one package. So
-there might be still references to sockets in the code, but they are of
-historical nature and should be cleaned up.
-
-The topology of a system is described in the units of:
-
- - packages
- - cores
- - threads
-
-* Package:
-
- Packages contain a number of cores plus shared resources, e.g. DRAM
- controller, shared caches etc.
-
- AMD nomenclature for package is 'Node'.
-
- Package-related topology information in the kernel:
-
- - cpuinfo_x86.x86_max_cores:
-
- The number of cores in a package. This information is retrieved via CPUID.
-
- - cpuinfo_x86.phys_proc_id:
-
- The physical ID of the package. This information is retrieved via CPUID
- and deduced from the APIC IDs of the cores in the package.
-
- - cpuinfo_x86.logical_id:
-
- The logical ID of the package. As we do not trust BIOSes to enumerate the
- packages in a consistent way, we introduced the concept of logical package
- ID so we can sanely calculate the number of maximum possible packages in
- the system and have the packages enumerated linearly.
-
- - topology_max_packages():
-
- The maximum possible number of packages in the system. Helpful for per
- package facilities to preallocate per package information.
-
- - cpu_llc_id:
-
- A per-CPU variable containing:
- - On Intel, the first APIC ID of the list of CPUs sharing the Last Level
- Cache
-
- - On AMD, the Node ID or Core Complex ID containing the Last Level
- Cache. In general, it is a number identifying an LLC uniquely on the
- system.
-
-* Cores:
-
- A core consists of 1 or more threads. It does not matter whether the threads
- are SMT- or CMT-type threads.
-
- AMDs nomenclature for a CMT core is "Compute Unit". The kernel always uses
- "core".
-
- Core-related topology information in the kernel:
-
- - smp_num_siblings:
-
- The number of threads in a core. The number of threads in a package can be
- calculated by:
-
- threads_per_package = cpuinfo_x86.x86_max_cores * smp_num_siblings
-
-
-* Threads:
-
- A thread is a single scheduling unit. It's the equivalent to a logical Linux
- CPU.
-
- AMDs nomenclature for CMT threads is "Compute Unit Core". The kernel always
- uses "thread".
-
- Thread-related topology information in the kernel:
-
- - topology_core_cpumask():
-
- The cpumask contains all online threads in the package to which a thread
- belongs.
-
- The number of online threads is also printed in /proc/cpuinfo "siblings."
-
- - topology_sibling_cpumask():
-
- The cpumask contains all online threads in the core to which a thread
- belongs.
-
- - topology_logical_package_id():
-
- The logical package ID to which a thread belongs.
-
- - topology_physical_package_id():
-
- The physical package ID to which a thread belongs.
-
- - topology_core_id();
-
- The ID of the core to which a thread belongs. It is also printed in /proc/cpuinfo
- "core_id."
-
-
-
-System topology examples
-
-Note:
-
-The alternative Linux CPU enumeration depends on how the BIOS enumerates the
-threads. Many BIOSes enumerate all threads 0 first and then all threads 1.
-That has the "advantage" that the logical Linux CPU numbers of threads 0 stay
-the same whether threads are enabled or not. That's merely an implementation
-detail and has no practical impact.
-
-1) Single Package, Single Core
-
- [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
-
-2) Single Package, Dual Core
-
- a) One thread per core
-
- [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
- -> [core 1] -> [thread 0] -> Linux CPU 1
-
- b) Two threads per core
-
- [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
- -> [thread 1] -> Linux CPU 1
- -> [core 1] -> [thread 0] -> Linux CPU 2
- -> [thread 1] -> Linux CPU 3
-
- Alternative enumeration:
-
- [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
- -> [thread 1] -> Linux CPU 2
- -> [core 1] -> [thread 0] -> Linux CPU 1
- -> [thread 1] -> Linux CPU 3
-
- AMD nomenclature for CMT systems:
-
- [node 0] -> [Compute Unit 0] -> [Compute Unit Core 0] -> Linux CPU 0
- -> [Compute Unit Core 1] -> Linux CPU 1
- -> [Compute Unit 1] -> [Compute Unit Core 0] -> Linux CPU 2
- -> [Compute Unit Core 1] -> Linux CPU 3
-
-4) Dual Package, Dual Core
-
- a) One thread per core
-
- [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
- -> [core 1] -> [thread 0] -> Linux CPU 1
-
- [package 1] -> [core 0] -> [thread 0] -> Linux CPU 2
- -> [core 1] -> [thread 0] -> Linux CPU 3
-
- b) Two threads per core
-
- [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
- -> [thread 1] -> Linux CPU 1
- -> [core 1] -> [thread 0] -> Linux CPU 2
- -> [thread 1] -> Linux CPU 3
-
- [package 1] -> [core 0] -> [thread 0] -> Linux CPU 4
- -> [thread 1] -> Linux CPU 5
- -> [core 1] -> [thread 0] -> Linux CPU 6
- -> [thread 1] -> Linux CPU 7
-
- Alternative enumeration:
-
- [package 0] -> [core 0] -> [thread 0] -> Linux CPU 0
- -> [thread 1] -> Linux CPU 4
- -> [core 1] -> [thread 0] -> Linux CPU 1
- -> [thread 1] -> Linux CPU 5
-
- [package 1] -> [core 0] -> [thread 0] -> Linux CPU 2
- -> [thread 1] -> Linux CPU 6
- -> [core 1] -> [thread 0] -> Linux CPU 3
- -> [thread 1] -> Linux CPU 7
-
- AMD nomenclature for CMT systems:
-
- [node 0] -> [Compute Unit 0] -> [Compute Unit Core 0] -> Linux CPU 0
- -> [Compute Unit Core 1] -> Linux CPU 1
- -> [Compute Unit 1] -> [Compute Unit Core 0] -> Linux CPU 2
- -> [Compute Unit Core 1] -> Linux CPU 3
-
- [node 1] -> [Compute Unit 0] -> [Compute Unit Core 0] -> Linux CPU 4
- -> [Compute Unit Core 1] -> Linux CPU 5
- -> [Compute Unit 1] -> [Compute Unit Core 0] -> Linux CPU 6
- -> [Compute Unit Core 1] -> Linux CPU 7
--
2.20.1