memcontrol(8) [freebsd man page]

MEMCONTROL(8)						    BSD System Manager's Manual 					     MEMCONTROL(8)

NAME

     memcontrol -- control system cache behaviour with respect to memory

SYNOPSIS

     memcontrol list [-a]
     memcontrol set -b base -l length -o owner attribute
     memcontrol clear -o owner
     memcontrol clear -b base -l length

DESCRIPTION

     A number of supported system architectures allow the behaviour of the CPU cache to be programmed to behave differently depending on the
     region being written.

     The memcontrol utility provides an interface to this facility, allowing CPU cache behavior to be altered for ranges of system physical mem-
     ory.

     These ranges are typically power-of-2 aligned and sized, however the specific rules governing their layout vary between architectures.  The
     memcontrol utility does not attempt to enforce these rules, however the system will reject any attempt to set an illegal combination.

     list   List range slots.

	    -a	    List all range slots, even those that are inactive.

     set    Set memory range attributes.

	    -b base
		    Memory range base address.

	    -l length
		    Length of memory range in bytes, power of 2.

	    -o owner
		    Text identifier for this setting (7 char max).

	    attribute
		    Attributes applied to this range; combinations of force, uncacheable, write-combine, write-through, write-back, and
		    write-protect.

     clear  Clear memory range attributes.  Ranges may be cleared by owner or by base/length combination.

	    To clear based on ownership:

	    -o owner
		    All ranges with this owner will be cleared.

	    To clear based on the base/length combination:

	    -b base
		    Memory range base address.

	    -l length
		    Length of memory range in bytes, power of 2.

	    Base and length must exactly match an existing range.

SEE ALSO

     mem(4)

BSD
								September 15, 2002							       BSD

I386_GET_MTRR(2)					   BSD/i386 System Calls Manual 					  I386_GET_MTRR(2)

NAME

     i386_get_mtrr, i386_set_mtrr -- access Memory Type Range Registers

LIBRARY

     i386 Architecture Library (libi386, -li386)

SYNOPSIS

     #include <sys/types.h>
     #include <machine/sysarch.h>
     #include <machine/mtrr.h>

     int
     i386_get_mtrr(struct mtrr *mtrrp, int *n);

     int
     i386_set_mtrr(struct mtrr *mtrrp, int *n);

DESCRIPTION

     These functions provide an interface to the MTRR registers found on 686-class processors for controlling processor access to memory ranges.
     This is most useful for accessing devices such as video accelerators on pci(4) and agp(4) buses.  For example, enabling write-combining
     allows bus-write transfers to be combined into a larger transfer before bursting over the bus.  This can increase performance of write opera-
     tions 2.5 times or more.

     mtrrp is a pointer to one or more mtrr structures, as described below.  The n argument is a pointer to an integer containing the number of
     structures pointed to by mtrrp.  For i386_set_mtrr() the integer pointed to by n will be updated to reflect the actual number of MTRRs suc-
     cessfully set.  For i386_get_mtrr() no more than n structures will be copied out, and the integer value pointed to by n will be updated to
     reflect the actual number of valid structures retrieved.  A NULL argument to mtrrp will result in just the number of MTRRs available being
     returned in the integer pointed to by n.

     The argument mtrrp has the following structure:

     struct mtrr {
	     uint64_t base;
	     uint64_t len;
	     uint8_t type;
	     int flags;
	     pid_t owner;
     };

     The location of the mapping is described by its physical base address base and length len.  Valid values for type are:

	   MTRR_TYPE_UC      uncached memory
	   MTRR_TYPE_WC      use write-combining
	   MTRR_TYPE_WT      use write-through caching
	   MTRR_TYPE_WP      write-protected memory
	   MTRR_TYPE_WB      use write-back caching

     Valid values for flags are:

	   MTRR_PRIVATE  own range, reset the MTRR when the current process exits
	   MTRR_FIXED	 use fixed range MTRR
	   MTRR_VALID	 entry is valid

     The owner member is the PID of the user process which claims the mapping.	It is only valid if MTRR_PRIVATE is set in flags.  To clear/reset
     MTRRs, use a flags field without MTRR_VALID set.

RETURN VALUES

     Upon successful completion zero is returned, otherwise -1 is returned on failure, and the global variable errno is set to indicate the error.
     The integer value pointed to by n will contain the number of successfully processed mtrr structures in both cases.

ERRORS

     [ENOSYS]  The currently running kernel or CPU has no MTRR support.

     [EINVAL]  The currently running kernel has no MTRR support, or one of the mtrr structures pointed to by mtrrp is invalid.

     [EBUSY]   No unused MTRRs are available.

HISTORY

     The i386_get_mtrr() and i386_set_mtrr() functions appeared in NetBSD 1.6.

BSD
								 November 10, 2001							       BSD