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man pages section 2: System Calls

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Updated: Thursday, June 13, 2019
 
 

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 addresses to be examined; the maximum number of addresses that can be processed for each call is MAX_MEMINFO_CNT

addr_count

number of addresses to be examined. Request sizes exceeding MAX_MEMINFO_CNT are not examined atomically and thus may not be self-consistent.

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 (requires PRIV_ALL)

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

MEMINFO_VADI

ADI status for the specified virtual address. 0=ADI disabled, 1=ADI enabled.

For all types of information except MEMINFO_VADI, any addresses in the inaddr array that have never been referenced will not have any information about them returned by meminfo(). This can also occur if an address has not been referenced recently and the physical page that had been backing that address has been paged out. Information for MEMINFO_VADI is always returned.

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.

ENOTSUP

MEMINFO_VADI is specified, and ADI is not supported by the platform.

MEMINFO_VADI is specified, and the caller is a 32-bit process.

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(7) for descriptions of the following attributes:

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

See Also

memcntl(2), mmap(2), gethomelgroup(3C), getpagesize(3C), madvise(3C), sysconf(3C), attributes(7)