On Wed, Apr 24, 2019 at 02:44:07PM -0300, Mauro Carvalho Chehab wrote: > Em Wed, 24 Apr 2019 00:29:08 +0800 > Changbin Du <changbin.du@xxxxxxxxx> escreveu: > > > 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@xxxxxxxxx> > > --- > > 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 > > Why? Please preserve as much as possible from the original file... > it is really hard to see what you're doing. Most of those x86 > files are already almost at ReST format (like this one). There's > absolutely **no reason** why you would do so much radical changes > that would below the 50% similarity threshold that would make git > to recognize as a change on the same file! > My editor changed the indent. I need to redo this conversion. Thanks. > I'll give a quick review on this one, but it is really hard to be > sure that something is missing, when the similarity is too low. > > > > > 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@xxxxxxxxxxxxx> and Borislav Petkov <bp@xxxxxxxxx>. > > + > > +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 > > +:: > > I would just place the :: on the above line. Same applies to similar > cases on this file. > Sure. > > + > > + [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 > > Something got broken here. > > > + > > + 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 > > And here... This one, for example, should be, instead: > > [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 > > Clearly there's something that it is messing with tabs on your > x86 conversion. > Sorry for such mistake. I will check them one by one. > I'll stop my review here, as it sounds pointless to review it, > as there are too many broken whitespace stuff on your > conversion. > > Thanks, > Mauro -- Cheers, Changbin Du
