diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/filesystems/cramfs.txt | 2 | ||||
| -rw-r--r-- | Documentation/filesystems/tmpfs.txt | 2 | ||||
| -rw-r--r-- | Documentation/filesystems/vfs.txt | 4 | ||||
| -rw-r--r-- | Documentation/networking/switchdev.txt | 2 | ||||
| -rw-r--r-- | Documentation/x86/topology.txt | 208 |
5 files changed, 213 insertions, 5 deletions
diff --git a/Documentation/filesystems/cramfs.txt b/Documentation/filesystems/cramfs.txt index 31f53f0ab957..4006298f6707 100644 --- a/Documentation/filesystems/cramfs.txt +++ b/Documentation/filesystems/cramfs.txt @@ -38,7 +38,7 @@ the update lasts only as long as the inode is cached in memory, after which the timestamp reverts to 1970, i.e. moves backwards in time. Currently, cramfs must be written and read with architectures of the -same endianness, and can be read only by kernels with PAGE_CACHE_SIZE +same endianness, and can be read only by kernels with PAGE_SIZE == 4096. At least the latter of these is a bug, but it hasn't been decided what the best fix is. For the moment if you have larger pages you can just change the #define in mkcramfs.c, so long as you don't diff --git a/Documentation/filesystems/tmpfs.txt b/Documentation/filesystems/tmpfs.txt index d392e1505f17..d9c11d25bf02 100644 --- a/Documentation/filesystems/tmpfs.txt +++ b/Documentation/filesystems/tmpfs.txt @@ -60,7 +60,7 @@ size: The limit of allocated bytes for this tmpfs instance. The default is half of your physical RAM without swap. If you oversize your tmpfs instances the machine will deadlock since the OOM handler will not be able to free that memory. -nr_blocks: The same as size, but in blocks of PAGE_CACHE_SIZE. +nr_blocks: The same as size, but in blocks of PAGE_SIZE. nr_inodes: The maximum number of inodes for this instance. The default is half of the number of your physical RAM pages, or (on a machine with highmem) the number of lowmem RAM pages, diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt index b02a7d598258..4164bd6397a2 100644 --- a/Documentation/filesystems/vfs.txt +++ b/Documentation/filesystems/vfs.txt @@ -708,9 +708,9 @@ struct address_space_operations { from the address space. This generally corresponds to either a truncation, punch hole or a complete invalidation of the address space (in the latter case 'offset' will always be 0 and 'length' - will be PAGE_CACHE_SIZE). Any private data associated with the page + will be PAGE_SIZE). Any private data associated with the page should be updated to reflect this truncation. If offset is 0 and - length is PAGE_CACHE_SIZE, then the private data should be released, + length is PAGE_SIZE, then the private data should be released, because the page must be able to be completely discarded. This may be done by calling the ->releasepage function, but in this case the release MUST succeed. diff --git a/Documentation/networking/switchdev.txt b/Documentation/networking/switchdev.txt index fad63136ee3e..2f659129694b 100644 --- a/Documentation/networking/switchdev.txt +++ b/Documentation/networking/switchdev.txt @@ -386,7 +386,7 @@ used. First phase is to "prepare" anything needed, including various checks, memory allocation, etc. The goal is to handle the stuff that is not unlikely to fail here. The second phase is to "commit" the actual changes. -Switchdev provides an inftrastructure for sharing items (for example memory +Switchdev provides an infrastructure for sharing items (for example memory allocations) between the two phases. The object created by a driver in "prepare" phase and it is queued up by: diff --git a/Documentation/x86/topology.txt b/Documentation/x86/topology.txt new file mode 100644 index 000000000000..06afac252f5b --- /dev/null +++ b/Documentation/x86/topology.txt @@ -0,0 +1,208 @@ +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. + + +* 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_mask(): + + 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 |