numa.3

.\" Copyright 2003,2004 Andi Kleen, SuSE Labs.
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.\" entire resulting derived work is distributed under the terms of a
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.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein.
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.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.TH NUMA 3 "December 2007" "SuSE Labs" "Linux Programmer's Manual"
.SH NAME
numa \- NUMA policy library
.SH SYNOPSIS
.B #include <numa.h>
.sp
.B cc ... \-lnuma
.sp
.B int numa_available(void);
.sp
.BI "int numa_max_possible_node(void);"
.br
.BI "int numa_num_possible_nodes();"
.sp
.B int numa_max_node(void);
.br
.BI "int numa_num_configured_nodes();"
.br
.B struct bitmask *numa_get_mems_allowed(void);
.sp
.BI "int numa_num_configured_cpus(void);"
.br
.BI "struct bitmask *numa_all_nodes_ptr;"
.br
.BI "struct bitmask *numa_no_nodes_ptr;"
.br
.BI "struct bitmask *numa_all_cpus_ptr;"
.sp
.BI "int numa_num_task_cpus();"
.br
.BI "int numa_num_task_nodes();"
.sp
.BI "int numa_parse_bitmap(char *" line " , struct bitmask *" mask ");
.br
.BI "struct bitmask *numa_parse_nodestring(const char *" string );
.br
.BI "struct bitmask *numa_parse_nodestring_all(const char *" string );
.br
.BI "struct bitmask *numa_parse_cpustring(const char *" string );
.br
.BI "struct bitmask *numa_parse_cpustring_all(const char *" string );
.sp
.BI "long long numa_node_size(int " node ", long long*" freep );
.br
.BI "long long numa_node_size64(int " node ", long long *" freep );
.sp
.B int numa_preferred(void);
.br
.B int numa_has_preferred_many(void);
.br
.B struct bitmask *numa_preferred_many(void);
.br
.BI "void numa_set_preferred(int " node );
.br
.BI "void numa_set_preferred_many(struct bitmask *" nodemask );
.br
.BI "int numa_get_interleave_node(void);
.br
.B struct bitmask *numa_get_interleave_mask(void);
.br
.BI "void numa_set_interleave_mask(struct bitmask *" nodemask );
.br
.BI "void numa_interleave_memory(void *" start ", size_t " size ", struct bitmask *" nodemask );
.br
.BI "void numa_bind(struct bitmask *" nodemask );
.br
.BI "void numa_set_localalloc(void);
.br
.BI "void numa_set_membind(struct bitmask *" nodemask );
.br
.BI "void numa_set_membind_balancing(struct bitmask *" nodemask );
.br
.B struct bitmask *numa_get_membind(void);
.sp
.BI "void *numa_alloc_onnode(size_t " size ", int " node );
.br
.BI "void *numa_alloc_local(size_t " size );
.br
.BI "void *numa_alloc_interleaved(size_t " size );
.br
.BI "void *numa_alloc_interleaved_subset(size_t " size ",  struct bitmask *" nodemask );
.BI "void *numa_alloc(size_t " size );
.br
.BI "void *numa_realloc(void *"old_addr ", size_t " old_size ", size_t " new_size );
.br
.BI "void numa_free(void *" start ", size_t " size );
.sp
.BI "int numa_run_on_node(int " node );
.br
.BI "int numa_run_on_node_mask(struct bitmask *" nodemask );
.br
.BI "int numa_run_on_node_mask_all(struct bitmask *" nodemask );
.br
.B struct bitmask *numa_get_run_node_mask(void);
.sp
.BI "void numa_tonode_memory(void *" start ", size_t " size ", int " node );
.br
.BI "void numa_tonodemask_memory(void *" start ", size_t " size ", struct bitmask *" nodemask );
.br
.BI "void numa_setlocal_memory(void *" start ", size_t " size );
.br
.BI "void numa_police_memory(void *" start ", size_t " size );
.br
.BI "void numa_set_bind_policy(int " strict );
.br
.BI "void numa_set_strict(int " strict );
.sp
.\" should be undocumented ??
.BI "int numa_distance(int " node1 ", int " node2 );
.sp
.BI "int numa_sched_getaffinity(pid_t " pid ", struct bitmask *" mask );
.br
.BI "int numa_sched_setaffinity(pid_t " pid ", struct bitmask *" mask );
.br
.BI "int numa_node_to_cpus(int " node ", struct bitmask *" mask ");
.br
.BI "void numa_node_to_cpu_update();"
.br
.BI "int numa_node_of_cpu(int " cpu ");
.sp
.BI "struct bitmask *numa_allocate_cpumask();"
.sp
.BI "void numa_free_cpumask();"
.br
.BI "struct bitmask *numa_allocate_nodemask();"
.sp
.BI "void numa_free_nodemask();"
.br
.BI "struct bitmask *numa_bitmask_alloc(unsigned int " n ");
.br
.BI "struct bitmask *numa_bitmask_clearall(struct bitmask *" bmp );
.br
.BI "struct bitmask *numa_bitmask_clearbit(struct bitmask *" bmp ", unsigned int " n );
.br
.BI "int numa_bitmask_equal(const struct bitmask *" bmp1 ", const struct bitmask *" bmp2 );
.br
.BI "void numa_bitmask_free(struct bitmask *" bmp );
.br
.BI "int numa_bitmask_isbitset(const struct bitmask *" bmp ", unsigned int " n ");"
.br
.BI "unsigned int numa_bitmask_nbytes(struct bitmask *" bmp );
.br
.BI "struct bitmask *numa_bitmask_setall(struct bitmask *" bmp );
.br
.BI "struct bitmask *numa_bitmask_setbit(struct bitmask *" bmp ", unsigned int " n );
.br
.BI "void copy_bitmask_to_nodemask(struct bitmask *" bmp ", nodemask_t *" nodemask )
.br
.BI "void copy_nodemask_to_bitmask(nodemask_t *" nodemask ", struct bitmask *" bmp )
.br
.BI "void copy_bitmask_to_bitmask(struct bitmask *" bmpfrom ", struct bitmask *" bmpto )
.br
.BI "unsigned int numa_bitmask_weight(const struct bitmask *bmp )
.sp
.BI "int numa_move_pages(int " pid ", unsigned long " count ", void **" pages ", const int *" nodes ", int *" status ", int " flags );
.br
.BI "int numa_migrate_pages(int " pid ", struct bitmask *" fromnodes ", struct bitmask *" tonodes );
.sp
.BI "void numa_error(char *" where );
.sp
.BI "extern int " numa_exit_on_error ;
.br
.BI "extern int " numa_exit_on_warn ;
.br
.BI "void numa_warn(int " number ", char *" where ", ...);"
.br

.SH DESCRIPTION
The
.I 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.
Furthermore, memory policies specified for a range of a shared memory
attached using
.I shmat(2)
or
.I 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
.BR 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
.B numa_alloc_*
functions take care of this automatically.

A
.I 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:
.IR numa_node_to_cpus (),
.IR numa_node_to_cpu_update (),
.IR numa_node_of_cpu (),
.IR numa_bind (),
.IR numa_run_on_node (),
.IR numa_run_on_node_mask (),
.IR numa_run_on_node_mask_all (),
and
.IR 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
.I numa_all_nodes_ptr
points to a bit mask that has all available nodes set;
.I numa_no_nodes_ptr
points to the empty set.

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

.BR 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
.BR numa_num_possible_nodes()
and subtracting 1.

.BR 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.

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

.BR 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)).

.BR 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.

.BR 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.

.BR 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
.BR numa_allocate_nodemask()
using size
.BR 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.

.BR 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
.BR numa_allocate_nodemask()
using size
.BR numa_max_possible_node().
The user should not alter this bitmask.

.BR 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
.BR numa_allocate_cpumask()
using size
.BR 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.

.BR 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
.BR numa_all_cpus_ptr.

.BR 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
.BR numa_all_nodes_ptr.

.BR numa_parse_bitmap()
parses
.I 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
.BR 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
.I libnuma
internally.

.BR numa_parse_nodestring()
parses a character string list of nodes into a bit mask.
The bit mask is allocated by
.BR 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 (
.BR numa_num_task_nodes()
) nodes.  Node numbers are limited by the number in the system.  See
.BR numa_max_node()
and
.BR numa_num_configured_nodes().
.br
Examples:  1-5,7,10   !4-5   +0-3
.br
If the string is of 0 length, bitmask
.BR numa_no_nodes_ptr
is returned.  Returns 0 if the string is invalid.

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

.BR numa_parse_cpustring()
parses a character string list of cpus into a bit mask.
The bit mask is allocated by
.BR 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 (
.BR numa_num_task_cpus()
) cpus.
Cpu numbers are limited by the number in the system.  See
.BR numa_num_task_cpus()
and
.BR numa_num_configured_cpus().
.br
Examples:  1-5,7,10   !4-5   +0-3
.br
Returns 0 if the string is invalid.

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

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

.BR numa_node_size64 ()
works the same as
.BR numa_node_size ().
This is useful on 32-bit architectures with large nodes.

.BR 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.
.\" TODO:   results are misleading for MPOL_PREFERRED and may
.\" be incorrect for MPOL_BIND when Mel Gorman's twozonelist
.\" patches go in.  In the latter case, we'd need to know the
.\" order of the current node's zonelist to return the correct
.\" node.  Need to tighten this up with the syscall results.

.BR numa_has_preferred_many ()
Returns > 0 if the system supports multiple preferred nodes.

.BR numa_preferred_many ()
Returns the current set of preferred nodes. This implies the empty set when the
policy isn't one used for preference
.I (PREFERRED, PREFERRED_MANY, BIND).
The caller is responsible for freeing the mask with
.BR numa_bitmask_free ().

.BR numa_set_preferred ()
sets the preferred node for the current task to
.IR 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
.I node
of \-1 argument specifies local allocation and is equivalent to
calling
.BR numa_set_localalloc ().

.BR numa_set_preferred_many ()
sets the preferred set of nodes for the current task to
.IR nodemask .
This is similar to
.BR numa_set_preferred ()
with the exception that it utilizes a different kernel interface to specify
multiple preferred nodes.
The caller is responsible for freeing the mask with
.BR numa_bitmask_free ().

.BR 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.

.BR numa_set_interleave_mask ()
sets the memory interleave mask for the current task to
.IR 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
.RI ( 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.
.\" NOTE:  the following is not really the case.  this function sets the
.\" task policy for all future allocations, including stack,  bss, ...
.\" The functions specified in this sentence actually allocate a new memory
.\" range [via mmap()].  This is quite a different thing.  Suggest we drop
.\" this.
.\" This is a low level
.\" function, it may be more convenient to use the higher level functions like
.\" .BR numa_alloc_interleaved ()
.\" or
.\" .BR numa_alloc_interleaved_subset ().

.BR numa_interleave_memory ()
interleaves
.I size
bytes of memory page by page from
.I start
on nodes specified in
.IR nodemask .
The
.I size
argument will be rounded up to a multiple of the system page size.
If
.I 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
.BR mmap (2)
or
.BR shmat (2),
but has not been accessed by the current process yet. The memory is page
interleaved to all nodes specified in
.IR nodemask .
Normally
.BR 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
.BR 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.

.BR numa_bind ()
binds the current task and its children to the nodes
specified in
.IR 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
.\" FIXME checkme
.\" This is the case.  --lts
.I numa_run_on_node_mask(nodemask)
followed by
.IR numa_set_membind(nodemask) .
If tasks should be bound to individual CPUs inside nodes
consider using
.I numa_node_to_cpus
and the
.I sched_setaffinity(2)
syscall.

.BR 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.

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

.BR numa_set_membind_balancing ()
sets the memory allocation mask and enable the Linux kernel NUMA
balancing for the task if the feature is supported by the kernel.
The task will only allocate memory from the nodes set in
.IR nodemask .
Passing an empty
.I nodemask
or a
.I nodemask
that contains nodes other than those in the mask returned by
.IR numa_get_mems_allowed ()
will result in an error.

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

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

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

.BR numa_alloc_interleaved ()
allocates
.I 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
.BR numa_free ().
On error, NULL is returned.

.BR numa_alloc_interleaved_subset ()
attempts to allocate
.I size
bytes of memory page interleaved on all nodes.
The
.I 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 compared to the
.IR 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
.BR numa_free ().
On error, NULL is returned.

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

.BR numa_realloc ()
changes the size of the memory area pointed to by
.I old_addr
from
.I old_size
to
.I new_size.
The memory area pointed to by
.I old_addr
must have been allocated with one of the
.BR numa_alloc*
functions.
The
.I 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
.BR 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
.BR 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
.I errno
is set to indicate the error. The pointer returned by
.BR numa_realloc ()
is suitable for passing to
.BR numa_free ().


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

.BR 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
.BR 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
.I errno
is set to indicate the error.

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

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

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

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

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

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

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

.BR 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
.I 2.6.10
or newer.

.BR 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.

.BR 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.

.BR numa_get_interleave_node()
is used by
.I 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).

.BR 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).

.BR numa_sched_getaffinity()
retrieves a bitmask of the cpus on which a task may run.  The task is
specified by
.I 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
.BR numa_allocate_cpumask()
to allocate it.
Test the bits in the mask by calling
.BR numa_bitmask_isbitset().

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

.BR 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
.I errno
will be set to
.I ERANGE
and \-1 returned. On success 0 is returned.

.BR numa_node_to_cpu_update ()
Mark cpus bitmask of all nodes stale, then get the latest bitmask by calling
.BR numa_node_to_cpus ()
This allows to update the libnuma state after a CPU hotplug event. The application
is in charge of detecting CPU hotplug events.

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

.BR 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
.BR numa_num_possible_cpus().
The bitmask is zero-filled.

.BR numa_free_cpumask
frees a cpumask previously allocate by
.I numa_allocate_cpumask.

.BR 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
.BR numa_num_possible_nodes().
The bitmask is zero-filled.

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

.BR 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
.I n
bits.  The bit mask is zero-filled.  The bitmask
structure points to the bit mask and contains the
.I n
value.

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

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

.BR 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.

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

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

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

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

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

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

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

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

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

.br
.BR 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.
.br
.I pid
- ID of task.  If not valid, use the current task.
.br
.I count
- Number of pages.
.br
.I pages
- List of pages to move.
.br
.I nodes
- List of nodes to which pages can be moved.
.br
.I status
- Field to which status is to be returned.
.br
.I flags
- MPOL_MF_MOVE or MPOL_MF_MOVE_ALL
.br
See move_pages(2).

.BR 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
.BR numa_allocate_nodemask()
, or with
.BR numa_bitmask_alloc()
using an
.I n
value returned from
.BR numa_num_possible_nodes().
A task's current node set can be gotten by calling
.BR numa_get_membind().
Bits in the
.I tonodes
mask can be set by calls to
.BR numa_bitmask_setbit().

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

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

.SH Compatibility with libnuma version 1
Binaries that were compiled for libnuma version 1 need not be re-compiled
to run with libnuma version 2.
.br
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

.SH THREAD SAFETY
.I numa_set_bind_policy
and
.I numa_exit_on_error
are process global. The other calls are thread safe.

.SH COPYRIGHT
Copyright 2002, 2004, 2007, 2008 Andi Kleen, SuSE Labs.
.I libnuma
is under the GNU Lesser General Public License, v2.1.

.SH SEE ALSO
.BR get_mempolicy (2),
.BR set_mempolicy (2),
.BR getpagesize (2),
.BR mbind (2),
.BR mmap (2),
.BR shmat (2),
.BR numactl (8),
.BR sched_getaffinity (2)
.BR sched_setaffinity (2)
.BR move_pages (2)
.BR migrate_pages (2)