phoenix-rtos-doc / libc / functions / m / meminfo.impl.md

meminfo

Synopsis

#include <sys/mman.h>

void meminfo(meminfo_t *info);

Description

The meminfo() function shall assign values for a meminfo_t structure. The meminfo_t implementation is presented below.

typedef struct _meminfo_t {
    struct {
        unsigned int alloc, free, boot, sz;
        int mapsz;
        pageinfo_t *map;
    } page;

    struct {
        unsigned int pid, total, free, sz;
        int mapsz, kmapsz;
        entryinfo_t *kmap, *map;
    } entry;
} meminfo_t;

The structure consists of two following parts: page and entry.

The page, in general, is a representation of RAM physical memory's part. For more information about paging technique please refer to the Memory management chapter and Page allocator chapter.

Each of the structure's elements has been briefly described:

alloc - Size of allocated pages in bytes,
free - Size of free pages in bytes,
boot - Size of pages reserved by the internal boot firmware in bytes,
sz - Size of the page_t structure which describes each physical page available,
mapsz - Number of all available pages, both free and allocated. It only applies to target architectures with MMU (memory management unit).
map - Array (in fact pointer to an array) with information about each of the available pages in pageinfo_t format.

If mapsz has been passed to the meminfo() function with -1 value mapsz and map won't be changed.

An entry describes one memory segment, and it's one abstraction layer higher than a page. Entries compose a memory map which is address space, for example, intended for kernel. Read more about memory mapping in Memory mapper chapter.

The entry structure consists of following elements:

pid - Mapper process ID,
total - Size of all available entries in bytes,
free - Size of free entries in bytes,
sz - Size of the map_entry_t structure which describes an entry,
mapsz - Number of all available entries,
kmapsz - Number of entries associated with kernel,
kmap - Array (in fact pointer to an array) with information about each of the entry associated with kernel in entryinfo_t format.
map - Array (in fact pointer to an array) with information about each of the available entries in entryinfo_t format.

If mapsz has been passed to the meminfo() function with -1 value mapsz and map won't be changed.

Similarly to mapsz, if kmapsz has been passed to the meminfo() function with -1 value kmapsz and kmap won't be changed.

Return value

The meminfo() function doesn't return anything.

Errors

No errors are defined.

Tests

Untested

Known bugs

None