Ubuntu Manpage: numa - NUMA policy library

Provided by: libnuma-dev_2.0.11-2.1ubuntu0.1_amd64

NAME

       numa - NUMA policy library

SYNOPSIS

       #include <numa.h>

       cc ... -lnuma

       int numa_available(void);

       int numa_max_possible_node(void);
       int numa_num_possible_nodes();

       int numa_max_node(void);
       int numa_num_configured_nodes();
       struct bitmask *numa_get_mems_allowed(void);

       int numa_num_configured_cpus(void);
       struct bitmask *numa_all_nodes_ptr;
       struct bitmask *numa_no_nodes_ptr;
       struct bitmask *numa_all_cpus_ptr;

       int numa_num_task_cpus();
       int numa_num_task_nodes();

       int numa_parse_bitmap(char *line , struct bitmask *mask);
       struct bitmask *numa_parse_nodestring(const char *string);
       struct bitmask *numa_parse_nodestring_all(const char *string);
       struct bitmask *numa_parse_cpustring(const char *string);
       struct bitmask *numa_parse_cpustring_all(const char *string);

       long numa_node_size(int node, long *freep);
       long long numa_node_size64(int node, long long *freep);

       int numa_preferred(void);
       void numa_set_preferred(int node);
       int numa_get_interleave_node(void);
       struct bitmask *numa_get_interleave_mask(void);
       void numa_set_interleave_mask(struct bitmask *nodemask);
       void numa_interleave_memory(void *start, size_t size, struct bitmask *nodemask);
       void numa_bind(struct bitmask *nodemask);
       void numa_set_localalloc(void);
       void numa_set_membind(struct bitmask *nodemask);
       struct bitmask *numa_get_membind(void);

       void *numa_alloc_onnode(size_t size, int node);
       void *numa_alloc_local(size_t size);
       void *numa_alloc_interleaved(size_t size);
       void  *numa_alloc_interleaved_subset(size_t  size,   struct  bitmask  *nodemask); void *numa_alloc(size_t
       size);
       void *numa_realloc(void *old_addr, size_t old_size, size_t new_size);
       void numa_free(void *start, size_t size);

       int numa_run_on_node(int node);
       int numa_run_on_node_mask(struct bitmask *nodemask);
       int numa_run_on_node_mask_all(struct bitmask *nodemask);
       struct bitmask *numa_get_run_node_mask(void);

       void numa_tonode_memory(void *start, size_t size, int node);
       void numa_tonodemask_memory(void *start, size_t size, struct bitmask *nodemask);
       void numa_setlocal_memory(void *start, size_t size);
       void numa_police_memory(void *start, size_t size);
       void numa_set_bind_policy(int strict);
       void numa_set_strict(int strict);

       int numa_distance(int node1, int node2);

       int numa_sched_getaffinity(pid_t pid, struct bitmask *mask);
       int numa_sched_setaffinity(pid_t pid, struct bitmask *mask);
       int numa_node_to_cpus(int node, struct bitmask *mask);
       int numa_node_of_cpu(int cpu);

       struct bitmask *numa_allocate_cpumask();

       void numa_free_cpumask();
       struct bitmask *numa_allocate_nodemask();

       void numa_free_nodemask();
       struct bitmask *numa_bitmask_alloc(unsigned int n);
       struct bitmask *numa_bitmask_clearall(struct bitmask *bmp);
       struct bitmask *numa_bitmask_clearbit(struct bitmask *bmp, unsigned int n);
       int numa_bitmask_equal(const struct bitmask *bmp1, const struct bitmask *bmp2);
       void numa_bitmask_free(struct bitmask *bmp);
       int numa_bitmask_isbitset(const struct bitmask *bmp, unsigned int n);
       unsigned int numa_bitmask_nbytes(struct bitmask *bmp);
       struct bitmask *numa_bitmask_setall(struct bitmask *bmp);
       struct bitmask *numa_bitmask_setbit(struct bitmask *bmp, unsigned int n);
       void copy_bitmask_to_nodemask(struct bitmask *bmp, nodemask_t *nodemask)
       void copy_nodemask_to_bitmask(nodemask_t *nodemask, struct bitmask *bmp)
       void copy_bitmask_to_bitmask(struct bitmask *bmpfrom, struct bitmask *bmpto)
       unsigned int numa_bitmask_weight(const struct bitmask *bmp )

       int numa_move_pages(int pid, unsigned long count, void  **pages,  const  int  *nodes,  int  *status,  int
       flags);
       int numa_migrate_pages(int pid, struct bitmask *fromnodes, struct bitmask *tonodes);

       void numa_error(char *where);

       extern int numa_exit_on_error;
       extern int numa_exit_on_warn;
       void numa_warn(int number, char *where, ...);

DESCRIPTION

The libnuma library offers a simple programming interface to the NUMA (Non Uniform Memory Access) policy
supported by the Linux kernel. On a NUMA architecture some memory areas have different latency or
bandwidth than others.

Available policies are page interleaving (i.e., allocate in a round-robin fashion from all, or a subset,
of the nodes on the system), preferred node allocation (i.e., preferably allocate on a particular node),
local allocation (i.e., allocate on the node on which the task is currently executing), or allocation
only on specific nodes (i.e., allocate on some subset of the available nodes). It is also possible to
bind tasks to specific nodes.

Numa memory allocation policy may be specified as a per-task attribute, that is inherited by children
tasks and processes, or as an attribute of a range of process virtual address space. Numa memory
policies specified for a range of virtual address space are shared by all tasks in the process. Further
more, memory policies specified for a range of a shared memory attached using shmat(2) or mmap(2) from
shmfs/hugetlbfs are shared by all processes that attach to that region. Memory policies for shared disk
backed file mappings are currently ignored.

The default memory allocation policy for tasks and all memory range is local allocation. This assumes
that no ancestor has installed a non-default policy.

For setting a specific policy globally for all memory allocations in a process and its children it is
easiest to start it with the numactl(8) utility. For more finegrained policy inside an application this
library can be used.

All numa memory allocation policy only takes effect when a page is actually faulted into the address
space of a process by accessing it. The numa_alloc_* functions take care of this automatically.

A node is defined as an area where all memory has the same speed as seen from a particular CPU. A node
can contain multiple CPUs. Caches are ignored for this definition.

Most functions in this library are only concerned about numa nodes and their memory. The exceptions to
this are: numa_node_to_cpus(), numa_node_of_cpu(), numa_bind(), numa_run_on_node(),
numa_run_on_node_mask(), numa_run_on_node_mask_all(), and numa_get_run_node_mask(). These functions deal
with the CPUs associated with numa nodes. See the descriptions below for more information.

Some of these functions accept or return a pointer to struct bitmask. A struct bitmask controls a bit
map of arbitrary length containing a bit representation of nodes. The predefined variable
numa_all_nodes_ptr points to a bit mask that has all available nodes set; numa_no_nodes_ptr points to the
empty set.

Before any other calls in this library can be used numa_available() must be called. If it returns -1, all
other functions in this library are undefined.

numa_max_possible_node() returns the number of the highest possible node in a system. In other words,
the size of a kernel type nodemask_t (in bits) minus 1. This number can be gotten by calling
numa_num_possible_nodes() and subtracting 1.

numa_num_possible_nodes() returns the size of kernel's node mask (kernel type nodemask_t). In other
words, large enough to represent the maximum number of nodes that the kernel can handle. This will match
the kernel's MAX_NUMNODES value. This count is derived from /proc/self/status, field Mems_allowed.

numa_max_node() returns the highest node number available on the current system. (See the node numbers
in /sys/devices/system/node/ ). Also see numa_num_configured_nodes().

numa_num_configured_nodes() returns the number of memory nodes in the system. This count includes any
nodes that are currently disabled. This count is derived from the node numbers in
/sys/devices/system/node. (Depends on the kernel being configured with /sys (CONFIG_SYSFS)).

numa_get_mems_allowed() returns the mask of nodes from which the process is allowed to allocate memory in
it's current cpuset context. Any nodes that are not included in the returned bitmask will be ignored in
any of the following libnuma memory policy calls.

numa_num_configured_cpus() returns the number of cpus in the system. This count includes any cpus that
are currently disabled. This count is derived from the cpu numbers in /sys/devices/system/cpu. If the
kernel is configured without /sys (CONFIG_SYSFS=n) then it falls back to using the number of online cpus.

numa_all_nodes_ptr points to a bitmask that is allocated by the library with bits representing all nodes
on which the calling task may allocate memory. This set may be up to all nodes on the system, or up to
the nodes in the current cpuset. The bitmask is allocated by a call to numa_allocate_nodemask() using
size numa_max_possible_node(). The set of nodes to record is derived from /proc/self/status, field
"Mems_allowed". The user should not alter this bitmask.

numa_no_nodes_ptr points to a bitmask that is allocated by the library and left all zeroes. The bitmask
is allocated by a call to numa_allocate_nodemask() using size numa_max_possible_node(). The user should
not alter this bitmask.

numa_all_cpus_ptr points to a bitmask that is allocated by the library with bits representing all cpus on
which the calling task may execute. This set may be up to all cpus on the system, or up to the cpus in
the current cpuset. The bitmask is allocated by a call to numa_allocate_cpumask() using size
numa_num_possible_cpus(). The set of cpus to record is derived from /proc/self/status, field
"Cpus_allowed". The user should not alter this bitmask.

numa_num_task_cpus() returns the number of cpus that the calling task is allowed to use. This count is
derived from the map /proc/self/status, field "Cpus_allowed". Also see the bitmask numa_all_cpus_ptr.

numa_num_task_nodes() returns the number of nodes on which the calling task is allowed to allocate
memory. This count is derived from the map /proc/self/status, field "Mems_allowed". Also see the
bitmask numa_all_nodes_ptr.

numa_parse_bitmap() parses line , which is a character string such as found in
/sys/devices/system/node/nodeN/cpumap into a bitmask structure. The string contains the hexadecimal
representation of a bit map. The bitmask may be allocated with numa_allocate_cpumask(). Returns 0 on
success. Returns -1 on failure. This function is probably of little use to a user application, but it
is used by libnuma internally.

numa_parse_nodestring() parses a character string list of nodes into a bit mask. The bit mask is
allocated by numa_allocate_nodemask(). The string is a comma-separated list of node numbers or node
ranges. A leading ! can be used to indicate "not" this list (in other words, all nodes except this
list), and a leading + can be used to indicate that the node numbers in the list are relative to the
task's cpuset. The string can be "all" to specify all ( numa_num_task_nodes() ) nodes. Node numbers are
limited by the number in the system. See numa_max_node() and numa_num_configured_nodes().
Examples: 1-5,7,10 !4-5 +0-3
If the string is of 0 length, bitmask numa_no_nodes_ptr is returned. Returns 0 if the string is invalid.

numa_parse_nodestring_all() is similar to numa_parse_nodestring , but can parse all possible nodes, not
only current nodeset.

numa_parse_cpustring() parses a character string list of cpus into a bit mask. The bit mask is allocated
by numa_allocate_cpumask(). The string is a comma-separated list of cpu numbers or cpu ranges. A
leading ! can be used to indicate "not" this list (in other words, all cpus except this list), and a
leading + can be used to indicate that the cpu numbers in the list are relative to the task's cpuset.
The string can be "all" to specify all ( numa_num_task_cpus() ) cpus. Cpu numbers are limited by the
number in the system. See numa_num_task_cpus() and numa_num_configured_cpus().
Examples: 1-5,7,10 !4-5 +0-3
Returns 0 if the string is invalid.

numa_parse_cpustring_all() is similar to numa_parse_cpustring , but can parse all possible cpus, not only
current cpuset.

numa_node_size() returns the memory size of a node. If the argument freep is not NULL, it used to return
the amount of free memory on the node. On error it returns -1.

numa_node_size64() works the same as numa_node_size() except that it returns values as long long instead
of long. This is useful on 32-bit architectures with large nodes.

numa_preferred() returns the preferred node of the current task. This is the node on which the kernel
preferably allocates memory, unless some other policy overrides this.

numa_set_preferred() sets the preferred node for the current task to node. The system will attempt to
allocate memory from the preferred node, but will fall back to other nodes if no memory is available on
the the preferred node. Passing a node of -1 argument specifies local allocation and is equivalent to
calling numa_set_localalloc().

numa_get_interleave_mask() returns the current interleave mask if the task's memory allocation policy is
page interleaved. Otherwise, this function returns an empty mask.

numa_set_interleave_mask() sets the memory interleave mask for the current task to nodemask. All new
memory allocations are page interleaved over all nodes in the interleave mask. Interleaving can be turned
off again by passing an empty mask (numa_no_nodes). The page interleaving only occurs on the actual page
fault that puts a new page into the current address space. It is also only a hint: the kernel will fall
back to other nodes if no memory is available on the interleave target.

numa_interleave_memory() interleaves size bytes of memory page by page from start on nodes specified in
nodemask. The size argument will be rounded up to a multiple of the system page size. If nodemask
contains nodes that are externally denied to this process, this call will fail. This is a lower level
function to interleave allocated but not yet faulted in memory. Not yet faulted in means the memory is
allocated using mmap(2) or shmat(2), but has not been accessed by the current process yet. The memory is
page interleaved to all nodes specified in nodemask. Normally numa_alloc_interleaved() should be used
for private memory instead, but this function is useful to handle shared memory areas. To be useful the
memory area should be several megabytes at least (or tens of megabytes of hugetlbfs mappings) If the
numa_set_strict() flag is true then the operation will cause a numa_error if there were already pages in
the mapping that do not follow the policy.

numa_bind() binds the current task and its children to the nodes specified in nodemask. They will only
run on the CPUs of the specified nodes and only be able to allocate memory from them. This function is
equivalent to calling numa_run_on_node_mask(nodemask) followed by numa_set_membind(nodemask). If tasks
should be bound to individual CPUs inside nodes consider using numa_node_to_cpus and the
sched_setaffinity(2) syscall.

numa_set_localalloc() sets the memory allocation policy for the calling task to local allocation. In
this mode, the preferred node for memory allocation is effectively the node where the task is executing
at the time of a page allocation.

numa_set_membind() sets the memory allocation mask. The task will only allocate memory from the nodes
set in nodemask. Passing an empty nodemask or a nodemask that contains nodes other than those in the
mask returned by numa_get_mems_allowed() will result in an error.

numa_get_membind() returns the mask of nodes from which memory can currently be allocated. If the
returned mask is equal to numa_all_nodes, then memory allocation is allowed from all nodes.

numa_alloc_onnode() allocates memory on a specific node. The size argument will be rounded up to a
multiple of the system page size. if the specified node is externally denied to this process, this call
will fail. This function is relatively slow compared to the malloc(3), family of functions. The memory
must be freed with numa_free(). On errors NULL is returned.

numa_alloc_local() allocates size bytes of memory on the local node. The size argument will be rounded
up to a multiple of the system page size. This function is relatively slow compared to the malloc(3)
family of functions. The memory must be freed with numa_free(). On errors NULL is returned.

numa_alloc_interleaved() allocates size bytes of memory page interleaved on all nodes. This function is
relatively slow and should only be used for large areas consisting of multiple pages. The interleaving
works at page level and will only show an effect when the area is large. The allocated memory must be
freed with numa_free(). On error, NULL is returned.

numa_alloc_interleaved_subset() attempts to allocate size bytes of memory page interleaved on all nodes.
The size argument will be rounded up to a multiple of the system page size. The nodes on which a process
is allowed to allocate memory may be constrained externally. If this is the case, this function may
fail. This function is relatively slow compare to malloc(3), family of functions and should only be used
for large areas consisting of multiple pages. The interleaving works at page level and will only show an
effect when the area is large. The allocated memory must be freed with numa_free(). On error, NULL is
returned.

numa_alloc() allocates size bytes of memory with the current NUMA policy. The size argument will be
rounded up to a multiple of the system page size. This function is relatively slow compare to the
malloc(3) family of functions. The memory must be freed with numa_free(). On errors NULL is returned.

numa_realloc() changes the size of the memory area pointed to by old_addr from old_size to new_size. The
memory area pointed to by old_addr must have been allocated with one of the numa_alloc* functions. The
new_size will be rounded up to a multiple of the system page size. The contents of the memory area will
be unchanged to the minimum of the old and new sizes; newly allocated memory will be uninitialized. The
memory policy (and node bindings) associated with the original memory area will be preserved in the
resized area. For example, if the initial area was allocated with a call to numa_alloc_onnode(), then the
new pages (if the area is enlarged) will be allocated on the same node. However, if no memory policy was
set for the original area, then numa_realloc() cannot guarantee that the new pages will be allocated on
the same node. On success, the address of the resized area is returned (which might be different from
that of the initial area), otherwise NULL is returned and errno is set to indicate the error. The pointer
returned by numa_realloc() is suitable for passing to numa_free().

numa_free() frees size bytes of memory starting at start, allocated by the numa_alloc_* functions above.
The size argument will be rounded up to a multiple of the system page size.

numa_run_on_node() runs the current task and its children on a specific node. They will not migrate to
CPUs of other nodes until the node affinity is reset with a new call to numa_run_on_node_mask(). Passing
-1 permits the kernel to schedule on all nodes again. On success, 0 is returned; on error -1 is
returned, and errno is set to indicate the error.

numa_run_on_node_mask() runs the current task and its children only on nodes specified in nodemask. They
will not migrate to CPUs of other nodes until the node affinity is reset with a new call to
numa_run_on_node_mask() or numa_run_on_node(). Passing numa_all_nodes permits the kernel to schedule on
all nodes again. On success, 0 is returned; on error -1 is returned, and errno is set to indicate the
error.

numa_run_on_node_mask_all() runs the current task and its children only on nodes specified in nodemask
like numa_run_on_node_mask but without any cpuset awareness.

numa_get_run_node_mask() returns a mask of CPUs on which the current task is allowed to run.

numa_tonode_memory() put memory on a specific node. The constraints described for
numa_interleave_memory() apply here too.

numa_tonodemask_memory() put memory on a specific set of nodes. The constraints described for
numa_interleave_memory() apply here too.

numa_setlocal_memory() locates memory on the current node. The constraints described for
numa_interleave_memory() apply here too.

numa_police_memory() locates memory with the current NUMA policy. The constraints described for
numa_interleave_memory() apply here too.

numa_distance() reports the distance in the machine topology between two nodes. The factors are a
multiple of 10. It returns 0 when the distance cannot be determined. A node has distance 10 to itself.
Reporting the distance requires a Linux kernel version of 2.6.10 or newer.

numa_set_bind_policy() specifies whether calls that bind memory to a specific node should use the
preferred policy or a strict policy. The preferred policy allows the kernel to allocate memory on other
nodes when there isn't enough free on the target node. strict will fail the allocation in that case.
Setting the argument to specifies strict, 0 preferred. Note that specifying more than one node non
strict may only use the first node in some kernel versions.

numa_set_strict() sets a flag that says whether the functions allocating on specific nodes should use use
a strict policy. Strict means the allocation will fail if the memory cannot be allocated on the target
node. Default operation is to fall back to other nodes. This doesn't apply to interleave and default.

numa_get_interleave_node() is used by libnuma internally. It is probably not useful for user
applications. It uses the MPOL_F_NODE flag of the get_mempolicy system call, which is not intended for
application use (its operation may change or be removed altogether in future kernel versions). See
get_mempolicy(2).

numa_pagesize() returns the number of bytes in page. This function is simply a fast alternative to
repeated calls to the getpagesize system call. See getpagesize(2).

numa_sched_getaffinity() retrieves a bitmask of the cpus on which a task may run. The task is specified
by pid. Returns the return value of the sched_getaffinity system call. See sched_getaffinity(2). The
bitmask must be at least the size of the kernel's cpu mask structure. Use numa_allocate_cpumask() to
allocate it. Test the bits in the mask by calling numa_bitmask_isbitset().

numa_sched_setaffinity() sets a task's allowed cpu's to those cpu's specified in mask. The task is
specified by pid. Returns the return value of the sched_setaffinity system call. See
sched_setaffinity(2). You may allocate the bitmask with numa_allocate_cpumask(). Or the bitmask may be
smaller than the kernel's cpu mask structure. For example, call numa_bitmask_alloc() using a maximum
number of cpus from numa_num_configured_cpus(). Set the bits in the mask by calling
numa_bitmask_setbit().

numa_node_to_cpus() converts a node number to a bitmask of CPUs. The user must pass a bitmask structure
with a mask buffer long enough to represent all possible cpu's. Use numa_allocate_cpumask() to create
it. If the bitmask is not long enough errno will be set to ERANGE and -1 returned. On success 0 is
returned.

numa_node_of_cpu() returns the node that a cpu belongs to. If the user supplies an invalid cpu errno will
be set to EINVAL and -1 will be returned.

numa_allocate_cpumask () returns a bitmask of a size equal to the kernel's cpu mask (kernel type
cpumask_t). In other words, large enough to represent NR_CPUS cpus. This number of cpus can be gotten
by calling numa_num_possible_cpus(). The bitmask is zero-filled.

numa_free_cpumask frees a cpumask previously allocate by numa_allocate_cpumask.

numa_allocate_nodemask() returns a bitmask of a size equal to the kernel's node mask (kernel type
nodemask_t). In other words, large enough to represent MAX_NUMNODES nodes. This number of nodes can be
gotten by calling numa_num_possible_nodes(). The bitmask is zero-filled.

numa_free_nodemask() frees a nodemask previous allocated by numa_allocate_nodemask().

numa_bitmask_alloc() allocates a bitmask structure and its associated bit mask. The memory allocated for
the bit mask contains enough words (type unsigned long) to contain n bits. The bit mask is zero-filled.
The bitmask structure points to the bit mask and contains the n value.

numa_bitmask_clearall() sets all bits in the bit mask to 0. The bitmask structure points to the bit mask
and contains its size ( bmp ->size). The value of bmp is always returned. Note that
numa_bitmask_alloc() creates a zero-filled bit mask.

numa_bitmask_clearbit() sets a specified bit in a bit mask to 0. Nothing is done if the n value is
greater than the size of the bitmask (and no error is returned). The value of bmp is always returned.

numa_bitmask_equal() returns 1 if two bitmasks are equal. It returns 0 if they are not equal. If the
bitmask structures control bit masks of different sizes, the "missing" trailing bits of the smaller bit
mask are considered to be 0.

numa_bitmask_free() deallocates the memory of both the bitmask structure pointed to by bmp and the bit
mask. It is an error to attempt to free this bitmask twice.

numa_bitmask_isbitset() returns the value of a specified bit in a bit mask. If the n value is greater
than the size of the bit map, 0 is returned.

numa_bitmask_nbytes() returns the size (in bytes) of the bit mask controlled by bmp. The bit masks are
always full words (type unsigned long), and the returned size is the actual size of all those words.

numa_bitmask_setall() sets all bits in the bit mask to 1. The bitmask structure points to the bit mask
and contains its size ( bmp ->size). The value of bmp is always returned.

numa_bitmask_setbit() sets a specified bit in a bit mask to 1. Nothing is done if n is greater than the
size of the bitmask (and no error is returned). The value of bmp is always returned.

copy_bitmask_to_nodemask() copies the body (the bit map itself) of the bitmask structure pointed to by
bmp to the nodemask_t structure pointed to by the nodemask pointer. If the two areas differ in size, the
copy is truncated to the size of the receiving field or zero-filled.

copy_nodemask_to_bitmask() copies the nodemask_t structure pointed to by the nodemask pointer to the body
(the bit map itself) of the bitmask structure pointed to by the bmp pointer. If the two areas differ in
size, the copy is truncated to the size of the receiving field or zero-filled.

copy_bitmask_to_bitmask() copies the body (the bit map itself) of the bitmask structure pointed to by the
bmpfrom pointer to the body of the bitmask structure pointed to by the bmpto pointer. If the two areas
differ in size, the copy is truncated to the size of the receiving field or zero-filled.

numa_bitmask_weight() returns a count of the bits that are set in the body of the bitmask pointed to by
the bmp argument.

numa_move_pages() moves a list of pages in the address space of the currently executing or current
process. It simply uses the move_pages system call.
pid - ID of task. If not valid, use the current task.
count - Number of pages.
pages - List of pages to move.
nodes - List of nodes to which pages can be moved.
status - Field to which status is to be returned.
flags - MPOL_MF_MOVE or MPOL_MF_MOVE_ALL
See move_pages(2).

numa_migrate_pages() simply uses the migrate_pages system call to cause the pages of the calling task, or
a specified task, to be migated from one set of nodes to another. See migrate_pages(2). The bit masks
representing the nodes should be allocated with numa_allocate_nodemask() , or with numa_bitmask_alloc()
using an n value returned from numa_num_possible_nodes(). A task's current node set can be gotten by
calling numa_get_membind(). Bits in the tonodes mask can be set by calls to numa_bitmask_setbit().

numa_error() is a libnuma internal function that can be overridden by the user program. This function is
called with a char * argument when a libnuma function fails. Overriding the library internal definition
makes it possible to specify a different error handling strategy when a libnuma function fails. It does
not affect numa_available(). The numa_error() function defined in libnuma prints an error on stderr and
terminates the program if numa_exit_on_error is set to a non-zero value. The default value of
numa_exit_on_error is zero.

numa_warn() is a libnuma internal function that can be also overridden by the user program. It is called
to warn the user when a libnuma function encounters a non-fatal error. The default implementation prints
a warning to stderr. The first argument is a unique number identifying each warning. After that there is
a printf(3)-style format string and a variable number of arguments. numa_warn exits the program when
numa_exit_on_warn is set to a non-zero value. The default value of numa_exit_on_warn is zero.

Compatibility with libnuma version 1

       Binaries that were compiled for libnuma version 1 need not be re-compiled to run with libnuma version 2.
       Source codes written for libnuma version 1 may be re-compiled without change with version 2 installed. To
       do so, in the code's Makefile add this option to CFLAGS:  -DNUMA_VERSION1_COMPATIBILITY

THREAD SAFETY

       numa_set_bind_policy and numa_exit_on_error are process global. The other calls are thread safe.

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