meminfo(2) (man pages section 2: System Calls)

man pages section 2: System Calls

meminfo(2)

Name

meminfo– provide information about memory

Synopsis

#include <sys/types.h>
#include <sys/mman.h>

int meminfo(const uint64_t inaddr[], int addr_count,
     const uint_t info_req[], int info_count, uint64_t outdata[],
     uint_t validity[]);

Parameters

inaddr: array of input addresses; the maximum number of addresses that can be processed for each call is MAX_MEMINFO_CNT
addr_count: number of addresses
info_req: array of types of information requested
info_count: number of pieces of information requested for each address in inaddr
outdata: array into which results are placed; array size must be the product of info_count and addr_count
validity: array of size addr_count containing bitwise result codes; 0th bit evaluates validity of corresponding input address, 1st bit validity of response to first member of info_req, and so on

Description

The meminfo() function provides information about virtual and physical memory particular to the calling process. The user or developer of performance utilities can use this information to analyze system memory allocations and develop a better understanding of the factors affecting application performance.

The caller of meminfo() can obtain the following types of information about both virtual and physical memory.

MEMINFO_VPHYSICAL: physical address corresponding to virtual address
MEMINFO_VLGRP: locality group of physical page corresponding to virtual address
MEMINFO_VPAGESIZE: size of physical page corresponding to virtual address
MEMINFO_VREPLCNT: number of replicated physical pages corresponding to specified virtual address
MEMINFO_VREPL | n: nth physical replica of specified virtual address
MEMINFO_VREPL_LGRP | n: lgrp of nth physical replica of specified virtual address
MEMINFO_PLGRP: locality group of specified physical address

Return Values

Upon successful completion meminfo() returns 0. Otherwise -1 is returned and errno is set to indicate the error.

Errors

The meminfo() function will fail if:

EFAULT: The area pointed to by outdata or validity could not be written, or the data pointed to by info_req or inaddr could not be read.
EINVAL: The value of info_count is greater than 31 or less than 1, or the value of addr_count is less than 1.

Examples

Example 1 Print physical pages and page sizes corresponding to a set of virtual addresses.

The following example prints the physical pages and page sizes corresponding to a set of virtual addresses.

void
print_info(void **addrvec, int how_many)
{
    static const uint_t info[] = {
        MEMINFO_VPHYSICAL,
        MEMINFO_VPAGESIZE
    };

    int info_num = sizeof (info) / sizeof (info[0]);
    int i;

    uint64_t *inaddr = alloca(sizeof (uint64_t) * how_many);
    uint64_t *outdata = alloca(sizeof (uint64_t) * how_many * info_num);
    uint_t *validity = alloca(sizeof (uint_t) * how_many);

    for (i = 0; i < how_many; i++)
        inaddr[i] = (uint64_t)addrvec[i];

    if (meminfo(inaddr, how_many, info, info_num, outdata, 
                validity) < 0) {
        perror("meminfo");
        return;
    }

    for (i = 0; i < how_many; i++) {
        if ((validity[i] & 1) == 0)
            printf("address 0x%llx not part of address space\n",
                inaddr[i]);

        else if ((validity[i] & 2) == 0)
            printf("address 0x%llx has no physical page "
                "associated with it\n", inaddr[i]);

        else {
            char buff[80];
            if ((validity[i] & 4) == 0)
                strcpy(buff, "<Unknown>");
            else
                sprintf(buff, "%lld",
                    outdata[i * info_num + 1]);

            printf("address 0x%llx is backed by physical "
                "page 0x%llx of size %s\n",
                inaddr[i], outdata[i * info_num], buff);
        }
    }    
}

Attributes

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE	ATTRIBUTE VALUE
Interface Stability	Stable
MT-Level	Async-Signal-Safe