Provided by: libhwloc-doc_1.8-1ubuntu1_all bug

NAME

       CPU binding -

   Enumerations
       enum hwloc_cpubind_flags_t { HWLOC_CPUBIND_PROCESS, HWLOC_CPUBIND_THREAD,
           HWLOC_CPUBIND_STRICT, HWLOC_CPUBIND_NOMEMBIND }

   Functions
        int hwloc_set_cpubind (hwloc_topology_t topology, hwloc_const_cpuset_t set, int flags)
        int hwloc_get_cpubind (hwloc_topology_t topology, hwloc_cpuset_t set, int flags)
        int hwloc_set_proc_cpubind (hwloc_topology_t topology, hwloc_pid_t pid,
           hwloc_const_cpuset_t set, int flags)
        int hwloc_get_proc_cpubind (hwloc_topology_t topology, hwloc_pid_t pid, hwloc_cpuset_t
           set, int flags)
        int hwloc_set_thread_cpubind (hwloc_topology_t topology, hwloc_thread_t thread,
           hwloc_const_cpuset_t set, int flags)
        int hwloc_get_thread_cpubind (hwloc_topology_t topology, hwloc_thread_t thread,
           hwloc_cpuset_t set, int flags)
        int hwloc_get_last_cpu_location (hwloc_topology_t topology, hwloc_cpuset_t set, int
           flags)
        int hwloc_get_proc_last_cpu_location (hwloc_topology_t topology, hwloc_pid_t pid,
           hwloc_cpuset_t set, int flags)

Detailed Description

       It is often useful to call hwloc_bitmap_singlify() first so that a single CPU remains in
       the set. This way, the process will not even migrate between different CPUs. Some
       operating systems also only support that kind of binding.

       Note:
           Some operating systems do not provide all hwloc-supported mechanisms to bind
           processes, threads, etc. and the corresponding binding functions may fail. -1 is
           returned and errno is set to ENOSYS when it is not possible to bind the requested kind
           of object processes/threads. errno is set to EXDEV when the requested cpuset can not
           be enforced (e.g. some systems only allow one CPU, and some other systems only allow
           one NUMA node).

       The most portable version that should be preferred over the others, whenever possible, is

       * hwloc_set_cpubind(topology, set, 0),
       *

       as it just binds the current program, assuming it is single-threaded, or

       * hwloc_set_cpubind(topology, set, HWLOC_CPUBIND_THREAD),
       *

       which binds the current thread of the current program (which may be multithreaded).

       Note:
           To unbind, just call the binding function with either a full cpuset or a cpuset equal
           to the system cpuset.

           On some operating systems, CPU binding may have effects on memory binding, see
           HWLOC_CPUBIND_NOMEMBIND

       Running lstopo --top can be a very convenient tool to check how binding actually happened.

Enumeration Type Documentation

   enum hwloc_cpubind_flags_t
       Process/Thread binding flags. These bit flags can be used to refine the binding policy.

       The default (0) is to bind the current process, assumed to be single-threaded, in a non-
       strict way. This is the most portable way to bind as all operating systems usually provide
       it.

       Note:
           Not all systems support all kinds of binding. See the 'Detailed Description' section
           of CPU binding for a description of errors that can occur.

       Enumerator

       HWLOC_CPUBIND_PROCESS
              Bind all threads of the current (possibly) multithreaded process.

       HWLOC_CPUBIND_THREAD
              Bind current thread of current process.

       HWLOC_CPUBIND_STRICT
              Request for strict binding from the OS. By default, when the designated CPUs are
              all busy while other CPUs are idle, operating systems may execute the
              thread/process on those other CPUs instead of the designated CPUs, to let them
              progress anyway. Strict binding means that the thread/process will _never_ execute
              on other cpus than the designated CPUs, even when those are busy with other tasks
              and other CPUs are idle.

       Note:
           Depending on the operating system, strict binding may not be possible (e.g., the OS
           does not implement it) or not allowed (e.g., for an administrative reasons), and the
           function will fail in that case.

       When retrieving the binding of a process, this flag checks whether all its threads
       actually have the same binding. If the flag is not given, the binding of each thread will
       be accumulated.

       Note:
           This flag is meaningless when retrieving the binding of a thread.

       HWLOC_CPUBIND_NOMEMBIND
              Avoid any effect on memory binding. On some operating systems, some CPU binding
              function would also bind the memory on the corresponding NUMA node. It is often not
              a problem for the application, but if it is, setting this flag will make hwloc
              avoid using OS functions that would also bind memory. This will however reduce the
              support of CPU bindings, i.e. potentially return -1 with errno set to ENOSYS in
              some cases.

       This flag is only meaningful when used with functions that set the CPU binding. It is
       ignored when used with functions that get CPU binding information.

Function Documentation

    int hwloc_get_cpubind (hwloc_topology_ttopology, hwloc_cpuset_tset, intflags)
       Get current process or thread binding. Writes into set the physical cpuset which the
       process or thread (according to flags) was last bound to.

    int hwloc_get_last_cpu_location (hwloc_topology_ttopology, hwloc_cpuset_tset, intflags)
       Get the last physical CPU where the current process or thread ran. The operating system
       may move some tasks from one processor to another at any time according to their binding,
       so this function may return something that is already outdated.

       flags can include either HWLOC_CPUBIND_PROCESS or HWLOC_CPUBIND_THREAD to specify whether
       the query should be for the whole process (union of all CPUs on which all threads are
       running), or only the current thread. If the process is single-threaded, flags can be set
       to zero to let hwloc use whichever method is available on the underlying OS.

    int hwloc_get_proc_cpubind (hwloc_topology_ttopology, hwloc_pid_tpid, hwloc_cpuset_tset,
       intflags)
       Get the current physical binding of process pid.

       Note:
           hwloc_pid_t is pid_t on Unix platforms, and HANDLE on native Windows platforms.

           HWLOC_CPUBIND_THREAD can not be used in flags.

           As a special case on Linux, if a tid (thread ID) is supplied instead of a pid (process
           ID), the binding for that specific thread is returned.

    int hwloc_get_proc_last_cpu_location (hwloc_topology_ttopology, hwloc_pid_tpid,
       hwloc_cpuset_tset, intflags)
       Get the last physical CPU where a process ran. The operating system may move some tasks
       from one processor to another at any time according to their binding, so this function may
       return something that is already outdated.

       Note:
           hwloc_pid_t is pid_t on Unix platforms, and HANDLE on native Windows platforms.

           As a special case on Linux, if a tid (thread ID) is supplied instead of a pid (process
           ID) and HWLOC_CPUBIND_THREAD is passed in flags, the binding for that specific thread
           is returned.

    int hwloc_get_thread_cpubind (hwloc_topology_ttopology, hwloc_thread_tthread,
       hwloc_cpuset_tset, intflags)
       Get the current physical binding of thread tid.

       Note:
           hwloc_thread_t is pthread_t on Unix platforms, and HANDLE on native Windows platforms.

           HWLOC_CPUBIND_PROCESS can not be used in flags.

    int hwloc_set_cpubind (hwloc_topology_ttopology, hwloc_const_cpuset_tset, intflags)
       Bind current process or thread on cpus given in physical bitmap set.

       Returns:
           -1 with errno set to ENOSYS if the action is not supported

           -1 with errno set to EXDEV if the binding cannot be enforced

    int hwloc_set_proc_cpubind (hwloc_topology_ttopology, hwloc_pid_tpid,
       hwloc_const_cpuset_tset, intflags)
       Bind a process pid on cpus given in physical bitmap set.

       Note:
           hwloc_pid_t is pid_t on Unix platforms, and HANDLE on native Windows platforms.

           HWLOC_CPUBIND_THREAD can not be used in flags.

    int hwloc_set_thread_cpubind (hwloc_topology_ttopology, hwloc_thread_tthread,
       hwloc_const_cpuset_tset, intflags)
       Bind a thread thread on cpus given in physical bitmap set.

       Note:
           hwloc_thread_t is pthread_t on Unix platforms, and HANDLE on native Windows platforms.

           HWLOC_CPUBIND_PROCESS can not be used in flags.

Author

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