x86_64_get_mtrr(2) [netbsd man page]
X86_64_GET_MTRR(2) BSD/x86_64 System Calls Manual X86_64_GET_MTRR(2) NAME
x86_64_get_mtrr, x86_64_set_mtrr -- access Memory Type Range Registers LIBRARY
x86_64 Architecture Library (libx86_64, -lx86_64) SYNOPSIS
#include <sys/types.h> #include <machine/sysarch.h> #include <machine/mtrr.h> int x86_64_get_mtrr(struct mtrr *mtrrp, int *n); int x86_64_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 x86_64_set_mtrr() the integer pointed to by n will be updated to reflect the actual number of MTRRs suc- cessfully set. For x86_64_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 x86_64_get_mtrr() and x86_64_set_mtrr() were derived from their i386 counterparts, which appeared in NetBSD 1.6. BSD
November 10, 2001 BSD
Check Out this Related Man Page
PMC_CONTROL(2) BSD System Calls Manual PMC_CONTROL(2) NAME
pmc_control, pmc_get_info -- Hardware Performance Monitoring Interface LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <sys/pmc.h> int pmc_control(int ctr, int op, void *argp); int pmc_get_info(int ctr, int op, void *argp); DESCRIPTION
pmc_get_info() returns the number of counters in the system or information on a specified counter ctr. The possible values for op are: PMC_INFO_NCOUNTERS When querying the number of counters in the system, ctr is ignored and argp is of type int *. Upon return, the integer pointed to by argp will contain the number of counters that are available in the system. PMC_INFO_CPUCTR_TYPE When querying the type of a counter in the system, ctr refers to the counter being queried, and argp is of type int *. Upon return, the integer pointed to by argp will contain the implementation-dependent type of the specified counter. If ctr is -1, the integer pointed to by argp will contain the machine-dependent type describing the CPU or counter configuration. PMC_INFO_COUNTER_VALUE When querying the value of a counter in the system, ctr refers to the counter being queried, and argp is of type uint64_t *. Upon return, the 64-bit integer pointed to by argp will contain the value of the specified counter. PMC_INFO_ACCUMULATED_COUNTER_VALUE When querying the value of a counter in the system, ctr refers to the counter being queried, and argp is of type uint64_t *. Upon return, the 64-bit integer pointed to by argp will contain the sum of the accumulated values of specified counter in all exited sub- processes of the current process. pmc_control() manipulates the specified counter ctr in one of several fashions. The op parameter determines the action taken by the kernel and also the interpretation of the argp parameter. The possible values for op are: PMC_OP_START Starts the specified ctr running. It must be preceded by a call with PMC_OP_CONFIGURE. argp is ignored in this case and may be NULL. PMC_OP_STOP Stops the specified ctr from running. argp is ignored in this case and may be NULL. PMC_OP_CONFIGURE Configures the specified ctr prior to running. argp is a pointer to a struct pmc_counter_cfg. struct pmc_counter_cfg { pmc_evid_t event_id; pmc_ctr_t reset_value; uint32_t flags; }; event_id is the event ID to be counted. reset_value is a value to which the counter should be reset on overflow (if supported by the implementation). This is most useful when profiling (see PMC_OP_PROFSTART, below). This value is defined to be the number of counter ticks before the next overflow. So, to get a profiling tick on every hundredth data cache miss, set the event_id to the proper value for ``dcache-miss'' and set reset_value to 100. flags Currently unused. PMC_OP_PROFSTART Configures the specified ctr for use in profiling. argp is a pointer to a struct pmc_counter_cfg as in PMC_OP_CONFIGURE, above. This request allocates a kernel counter, which will fail if any process is using the requested counter. Not all implementations or coun- ters may support this option. PMC_OP_PROFSTOP Stops the specified ctr from being used for profiling. argp is ignored in this case and may be NULL. RETURN VALUES
A return value of 0 indicates that the call succeeded. Otherwise, -1 is returned and the global variable errno is set to indicate the error. ERRORS
Among the possible error codes from pmc_control() and pmc_get_info() are [EFAULT] The address specified for the argp is invalid. [ENXIO] Specified counter is not yet configured. [EINPROGRESS] PMC_OP_START was passed for a counter that is already running. [EINVAL] Specified counter was invalid. [EBUSY] If the requested counter is already in use--either by the current process or by the kernel. [ENODEV] If and only if the specified counter event is not valid for the specified counter when configuring a counter or starting profiling. [ENOMEM] If the kernel is unable to allocate memory. SEE ALSO
pmc(1), pmc(9) HISTORY
The pmc_control() and pmc_get_info() system calls appeared in NetBSD 2.0. BSD
October 27, 2005 BSD