NAME
cpuset, cpuset_version, cpuset_pin, cpuset_size, cpuset_where,
cpuset_unpin, cpuset_alloc, cpuset_free, cpuset_cpus_nbits,
cpuset_mems_nbits, cpuset_setcpus, cpuset_setmems, cpuset_set_iopt,
cpuset_set_sopt, cpuset_getcpus, cpuset_getmems, cpuset_cpus_weight,
cpuset_mems_weight, cpuset_get_iopt, cpuset_get_sopt, cpuset_localcpus,
cpuset_localmems, cpuset_cpumemdist, cpuset_cpu2node, cpuset_addr2node,
cpuset_create, cpuset_delete, cpuset_query, cpuset_modify,
cpuset_getcpusetpath, cpuset_cpusetofpid, cpuset_mountpoint,
cpuset_collides_exclusive, cpuset_nuke, cpuset_init_pidlist,
cpuset_pidlist_length, cpuset_get_pidlist, cpuset_freepidlist,
cpuset_move, cpuset_move_all, cpuset_move_cpuset_tasks, cpuset_migrate,
cpuset_migrate_all, cpuset_reattach, cpuset_open_memory_pressure,
cpuset_read_memory_pressure, cpuset_close_memory_pressure,
cpuset_c_rel_to_sys_cpu, cpuset_c_sys_to_rel_cpu,
cpuset_c_rel_to_sys_mem, cpuset_c_sys_to_rel_mem,
cpuset_p_rel_to_sys_cpu, cpuset_p_sys_to_rel_cpu,
cpuset_p_rel_to_sys_mem, cpuset_p_sys_to_rel_mem, cpuset_get_placement,
cpuset_equal_placement, cpuset_free_placement, cpuset_fts_open,
cpuset_fts_read, cpuset_fts_reverse, cpuset_fts_rewind,
cpuset_fts_get_path, cpuset_fts_get_stat, cpuset_fts_get_cpuset,
cpuset_fts_get_errno, cpuset_fts_get_info, cpuset_fts_close,
cpuset_cpubind, cpuset_latestcpu, cpuset_membind,
cpuset_get_cpu_affinity, cpuset_set_cpu_affinity,
cpuset_get_mem_affinity, cpuset_export, cpuset_import, cpuset_function
- Library for managing CPU and Memory placement.
SYNOPSIS
#include <bitmask.h>
#include <cpuset.h>
cc ... -lcpuset
Basic cpuset routines
int cpuset_pin(int relcpu);
int cpuset_size();
int cpuset_where();
int cpuset_unpin();
Basic cpuset routines (Fortran interface)
include ’cpusetf.h’
integer relcpu
irtn = cpuset_pin(relcpu)
irtn = cpuset_size()
irtn = cpuset_unpin()
irtn = cpuset_where()
Cpuset library version.
int cpuset_version();
Allocate and free ‘struct cpuset *‘:
struct cpuset *cpuset_alloc();
void cpuset_free(struct cpuset *cp);
Lengths of CPUs and Memory Nodes bitmasks - use to alloc them:
int cpuset_cpus_nbits();
int cpuset_mems_nbits();
Set various attributes of a cpuset:
int cpuset_setcpus(struct cpuset *cp, const struct bitmask *cpus);
void cpuset_setmems(struct cpuset *cp, const struct bitmask *mems);
int cpuset_set_iopt(struct cpuset *cp, const char *optname, int val);
int cpuset_set_sopt(struct cpuset *cp, const char *optname, const char *val);
Query various attributes of a cpuset:
int cpuset_getcpus(const struct cpuset *cp, struct bitmask *cpus);
int cpuset_getmems(const struct cpuset *cp, struct bitmask *mems);
int cpuset_cpus_weight(const struct cpuset *cp);
int cpuset_mems_weight(const struct cpuset *cp);
int cpuset_get_iopt(const struct cpuset *cp, const char *optname);
const char *cpuset_get_sopt(const struct cpuset *cp, const char *optname);
Local CPUs and Memory Nodes:
int cpuset_localcpus(const struct bitmask *mems, struct bitmask *cpus);
int cpuset_localmems(const struct bitmask *cpus, struct bitmask *mems);
unsigned int cpuset_cpumemdist(int cpu, int mem);
int cpuset_cpu2node(int cpu);
int cpuset_addr2node(void *addr);
Create, delete, query, modify, list and examine cpusets:
int cpuset_create(const char *path, const struct *cp);
int cpuset_delete(const char *path);
int cpuset_query(struct cpuset *cp, const char *path);
int cpuset_modify(const char *path, const struct *cp);
char *cpuset_getcpusetpath(pid_t pid, char *buf, size_t size);
int cpuset_cpusetofpid(struct cpuset *cp, int pid);
const char *cpuset_mountpoint();
int cpuset_collides_exclusive(const char *cpusetpath, const struct cpuset *cp);
int cpuset_nuke(const char *path, unsigned int seconds);
List tasks (pids) currently attached to a cpuset:
struct cpuset_pidlist *cpuset_init_pidlist(const char *path, int recurse);
int cpuset_pidlist_length(const struct cpuset_pidlist *pl);
pid_t cpuset_get_pidlist(const struct cpuset_pidlist *pl, int i);
void cpuset_freepidlist(struct cpuset_pidlist *pl);
Attach tasks to cpusets:
int cpuset_move(pid_t p, const char *path);
int cpuset_move_all(struct cpuset_pid_list *pl, const char *path);
int cpuset_move_cpuset_tasks(const char *fromrelpath, const char *torelpath);
int cpuset_migrate(pid_t pid, const char *path);
int cpuset_migrate_all(struct cpuset_pid_list *pl, const char *path);
int cpuset_reattach(const char *path);
Monitor memory pressure caused by tasks in a cpuset:
int cpuset_open_memory_pressure(const char *cpusetpath);
int cpuset_read_memory_pressure(int han);
void cpuset_close_memory_pressure(int han);
Converting relative and system CPU and Memory Node numbers:
int cpuset_c_rel_to_sys_cpu(const struct cpuset *cp, int relcpu);
int cpuset_c_sys_to_rel_cpu(const struct cpuset *cp, int cpu);
int cpuset_c_rel_to_sys_mem(const struct cpuset *cp, int relmem);
int cpuset_c_sys_to_rel_mem(const struct cpuset *cp, int mem);
int cpuset_p_rel_to_sys_cpu(pid_t pid, int relcpu);
int cpuset_p_sys_to_rel_cpu(pid_t pid, int cpu);
int cpuset_p_rel_to_sys_mem(pid_t pid, int relmem);
int cpuset_p_sys_to_rel_mem(pid_t pid, int mem);
Placement operations for detecting cpuset migration:
struct cpuset_placement *cpuset_get_placement(pid_t pid);
int cpuset_equal_placement(const struct cpuset_placement *plc1,
const struct cpuset_placement *plc2);
void cpuset_free_placement(struct cpuset_placement *plc);
Traverse a cpuset hierarchy:
struct cpuset_fts_tree *cpuset_fts_open(const char *cpusetpath);
const struct cpuset_fts_entry *cpuset_fts_read(
struct cpuset_fts_tree *cs_tree);
void cpuset_fts_reverse(struct cpuset_fts_tree *cs_tree);
void cpuset_fts_rewind(struct cpuset_fts_tree *cs_tree);
const char *cpuset_fts_get_path(
const struct cpuset_fts_entry *cs_entry);
const struct stat *cpuset_fts_get_stat(
const struct cpuset_fts_entry *cs_entry);
const struct cpuset *cpuset_fts_get_cpuset(
const struct cpuset_fts_entry *cs_entry);
int cpuset_fts_get_errno(
const struct cpuset_fts_entry *cs_entry);
int cpuset_fts_get_info(
const struct cpuset_fts_entry *cs_entry);
void cpuset_fts_close(struct cpuset_fts_tree *cs_tree);
Bind to a CPU or Memory Node within the current cpuset:
int cpuset_cpubind(int cpu);
int cpuset_latestcpu(pid_t pid);
int cpuset_membind(int mem);
Export settings to and import from Text Representation:
int cpuset_export(const struct cpuset *cp, char *buf, int buflen);
int cpuset_import(struct cpuset *cp, const char *file,
int *errlinenum_ptr, char *errmsg_bufptr, int errmsg_buflen);
Calling [optional] cpuset_* API routines:
cpuset_function(const char *function_name);
DESCRIPTION
Cpusets are named subsets of a systems CPUs and Memory Nodes. On large
SMP and NUMA systems, it is commonly necessary to control which
processes and threads can run on which CPUs and Memory Nodes. Such
placement can be used to improve overall system performance, and to
manage system utilization in accordance with appropriate policies.
This cpuset library provides the mechanisms needed to create, destroy
and manage cpusets, and to control the placement of processes and
threads within cpusets.
Though this library has many functions, most applications using it will
only need the few functions in the Basic Cpuset API. These basic
functions enable an application to manage CPU and Memory placement on
SMP and NUMA systems within existing cpusets.
The Advanced Cpuset API provides support for creating, destroying and
managing cpusets, and for more complex placement within cpusets.
Workload managers, batch processors and other system services can use
the Advanced Cpuset API in order to manage cpusets across an entire
system, or a dedicated portion of a system.
All functions are part of the same library, and fully interoperable. A
system imposed permission model ensures that one application will not
be able to make changes to the cpusets or placement of other
applications, outside of its currently allowed cpuset.
Basic Cpuset API
The Basic Cpuset API provides functions usable from C for processor and
memory placement within a cpuset.
The basic functions enable an application to place various threads of
its execution on specific CPUs within its current cpuset, and perform
related functions such as asking how large the current cpuset is, and
on which CPU within the current cpuset a thread is currently executing.
The basic cpuset_pin(int relcpu) function uses cpuset relative
numbering. In a cpuset of N CPUs, relcpu ranges from zero to N-1. All
functions in the Advanced Cpuset API use system wide CPU and Memory
Node numbering, to provide a consistent numbering regardless of cpuset
configuration.
Memory placement is done automatically by the basic functions, local to
the requested CPU. Threads may only be pinned on a single CPU, or
unpinned and allowed the run of the entire current cpuset. This avoids
the need to allocate and free the bitmasks required to specify a set of
several CPUs. The basic functions do not support creating or removing
cpusets, only the placement of threads within an existing cpuset. This
avoids the need to explicitly allocate and free cpuset structures.
Operations only apply to the current thread, avoiding the need to pass
the process id of the thread to be affected.
Basic Functions
The Basic Cpuset API supports the following functions.
int cpuset_pin(int relcpu);
Pin the current task to execute only on the CPU relcpu, which is
a relative CPU number within the current cpuset of that task.
Also automatically pin the memory allowed to be used by the
current task to the memory on that same node (as determined by
the advanced cpuset_cpu2node() function).
int cpuset_size();
Return the number of CPUs in the current tasks cpuset. The
relative CPU numbers that are passed to the cpuset_pin()
function and that are returned by the cpuset_where() function,
must be between 0 and N - 1 inclusive, where N is the value
returned by cpuset_size().
int cpuset_where();
Return the CPU number, relative to the current tasks cpuset, of
the CPU on which the current task most recently executed. If a
task is allowed to execute on more than one CPU, then there is
no guarantee that the task is still executing on the CPU
returned by cpuset_where, by the time that the user code obtains
the return value.
int cpuset_unpin();
Remove the CPU and Memory pinning affects of any previous
cpuset_pin call, allowing the current task to execute on any CPU
in its current cpuset and to allocate memory on any Memory Node
in its current cpuset.
ERRORS
ENOSYS Invoked on an operating system kernel that does not support
cpusets.
ENODEV Invoked on a system that supports cpusets, but when the cpuset
file system is not currently mounted at /dev/cpuset.
ENOMEM Insufficient memory is available.
EBUSY Attempted cpuset_delete() on a cpuset with attached tasks.
EBUSY Attempted cpuset_delete() on a cpuset with child cpusets.
ENOENT Attempted cpuset_create() in a parent cpuset that doesn’t exist.
EEXIST Attempted cpuset_create() for a cpuset that already exists.
EEXIST Attempted to rename() a cpuset to a name that already exists
ENOTDIR
Attempted to rename() a non-existant cpuset.
E2BIG Attempted a write(2) system call on a special cpuset file with
a length larger than some kernel determined upper limit on the
length of such writes.
ESRCH Attempted to cpuset_move() a non-existance task.
EACCES Attempted to cpuset_move() a task which one lacks permission to
move.
EACCES Attempted to write(2) a memory_pressure file.
ENOSPC Attempted to cpuset_move() a task to an empty cpuset.
EINVAL The relcpu argument to cpuset_pin() is out of range (not between
zero and cpuset_size() - 1).
EINVAL Attempted to change a cpuset in a way that would violate a
cpu_exclusive or mem_exclusive attribute of that cpuset or any
of its siblings.
EINVAL Attempted to write an empty cpus or mems bitmask to the kernel.
The kernel creates new cpusets (via mkdir) with empty cpus and
mems, and the user level cpuset and bitmask code works with
empty masks. But the kernel will not allow an empty bitmask (no
bits set) to be written to the special cpus and mems files of a
cpuset.
EIO Attempted to write(2) a string to a cpuset tasks file that does
not begin with an ASCII decimal integer.
EIO Attempted to rename(2) a cpuset outside of its current
directory.
ENOSPC Attempted to write(2) a list to a cpus file that did not include
any online cpus.
ENOSPC Attempted to write(2) a list to a mems file that did not include
any online memory nodes.
EACCES Attempted to add a cpu or mem to a cpuset that is not already in
its parent.
EACCES Attempted to set cpu_exclusive or mem_exclusive on a cpuset
whose parent lacks the same setting.
ENODEV The cpuset was removed by another task at the same time as a
write(2) was attempted on one of the special files in the cpuset
directory.
EBUSY Attempted to remove a cpu or mem from a cpuset that is also in a
child of that cpuset.
EFAULT Attempted to read or write a cpuset file using a buffer that was
outside your accessible address space.
ENAMETOOLONG
Attempted to read a /proc/pid/cpuset file for a cpuset path that
was longer than the kernel page size.
ENAMETOOLONG
Attempted to create a cpuset whose base directory name was
longer than 255 characters.
ENAMETOOLONG
Attempted to create a cpuset whose full pathname including
"/dev/cpuset" was longer than 4095 characters.
ENXIO Attempted to create a cpu_exclusive cpuset whose cpus covered
just part of one or more physical processor packages, such as
including just one of the two Cores on a package. For Linux
kernel version 2.6.16 on i386 and x86_64, this operation is
rejected with this error to avoid a fatal kernel bug.
Otherwise, this is a normal and supported operation.
EINVAL Specified a cpus or mems list to the kernel which included a
range with the second number smaller than the first number.
EINVAL Specified a cpus or mems list to the kernel which included an
invalid character in the string.
ERANGE Specified a cpus or mems list to the kernel which included a
number too large for the kernel to set in its bitmasks.
ETIME Time limit for cpuset_nuke() operation reached without
successful completion of operation.
ENOTEMPTY
Tasks remain after multiple attempts by
cpuset_move_cpuset_tasks() to move them to a different cpuset.
EPERM Lacked permission to kill (send a signal to) a task.
EPERM Lacked permission to read a cpuset or its files.
EPERM Attempted to unlink a per-cpuset file. Such files can not be
unlinked. They can only be removed by removing (rmdir) the
directory representing the cpuset that contains these files.
Advanced Cpuset API
For additional documentation on cpusets, and for details of the all the
other, advanced, routines, see
/usr/share/doc/packages/libcpuset/libcpuset.html and
/usr/share/doc/packages/libbitmask/libbitmask.html. These same
documents are available in plain text format as
/usr/share/doc/packages/libcpuset/libcpuset.txt and
/usr/share/doc/packages/libbitmask/libbitmask.txt.
SEE ALSO
libbitmask(3)
AUTHOR
pj@sgi.com (Paul Jackson)