Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
NUMA(4)		       FreeBSD Kernel Interfaces Manual		       NUMA(4)

NAME
     NUMA -- Non-Uniform Memory	Access

SYNOPSIS
     options MAXMEMDOM
     options NUMA

DESCRIPTION
     Non-Uniform Memory	Access is a computer architecture design which
     involves unequal costs between processors,	memory and IO devices in a
     given system.

     In	a NUMA architecture, the latency to access specific memory or IO
     devices depends upon which	processor the memory or	device is attached to.
     Accessing memory local to a processor is faster than accessing memory
     that is connected to one of the other processors.	FreeBSD	implements
     NUMA-aware	memory allocation policies.  By	default	it attempts to ensure
     that allocations are balanced across each domain.	Users may override the
     default domain selection policy using cpuset(1).

     NUMA support is enabled when the NUMA option is specified in the kernel
     configuration file.  Each platform	defines	the MAXMEMDOM constant,	which
     specifies the maximum number of supported NUMA domains.  This constant
     may be specified in the kernel configuration file.	 NUMA support can be
     disabled at boot time by setting the vm.numa.disabled tunable to 1.
     Other values for this tunable are currently ignored.

     Thread and	process	NUMA policies are controlled with the
     cpuset_getdomain(2) and cpuset_setdomain(2) syscalls.  The	cpuset(1) tool
     is	available for starting processes with a	non-default policy, or to
     change the	policy of an existing thread or	process.

     Systems with non-uniform access to	I/O devices may	mark those devices
     with the local VM domain identifier.  Drivers can find out	their local
     domain information	by calling bus_get_domain(9).

   MIB Variables
     The operation of NUMA is controlled and exposes information with these
     sysctl(8) MIB variables:

     vm.ndomains
	     The number	of VM domains which have been detected.

     vm.phys_locality
	     A table indicating	the relative cost of each VM domain to each
	     other.  A value of	10 indicates equal cost.  A value of -1	means
	     the locality map is not available or no locality information is
	     available.

     vm.phys_segs
	     The map of	physical memory, grouped by VM domain.

IMPLEMENTATION NOTES
     The current NUMA implementation is	VM-focused.  The hardware NUMA domains
     are mapped	into a contiguous, non-sparse VM domain	space, starting	from
     0.	 Thus, VM domain information (for example, the domain identifier) is
     not necessarily the same as is found in the hardware specific informa-
     tion.  Policy information is available in both struct thread and struct
     proc.

SEE ALSO
     cpuset(1),	cpuset_getaffinity(2), cpuset_setaffinity(2),
     bus_get_domain(9)

HISTORY
     NUMA first	appeared in FreeBSD 9.0	as a first-touch allocation policy
     with a fail-over to round-robin allocation	and was	not configurable.  It
     was then modified in FreeBSD 10.0 to implement a round-robin allocation
     policy and	was also not configurable.

     The numa_getaffinity(2) and numa_setaffinity(2) syscalls and the
     numactl(1)	tool first appeared in FreeBSD 11.0 and	were removed in
     FreeBSD 12.0.  The	current	implementation appeared	in FreeBSD 12.0.

AUTHORS
     This manual page written by Adrian	Chadd <adrian@FreeBSD.org>.

NOTES
     No	statistics are kept to indicate	how often NUMA allocation policies
     succeed or	fail.

FreeBSD	Ports 11.2	       October 22, 2018		    FreeBSD Ports 11.2

NAME | SYNOPSIS | DESCRIPTION | IMPLEMENTATION NOTES | SEE ALSO | HISTORY | AUTHORS | NOTES

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=numa&sektion=4&manpath=FreeBSD+12.0-RELEASE+and+Ports>

home | help