“释放未使用的内核内存"在哪里?来自? [英] Where does "Freeing unused kernel memory" come from?

问题描述

我经常看到从 dmesg 释放未使用的内核内存:xxxK(......)，但是我从没有从内核源代码中找到该日志.grep/rg的帮助.

I often see Freeing unused kernel memory: xxxK (......) from dmesg, but I can never find this log from kernel source code with the help of grep/rg.

它来自哪里?

推荐答案

该行文本不作为单个完整字符串存在，因此无法对它进行grep.
当 init/main.c 中的 free_initmem()调用 free_initmem_default()时，这一切都会滚动.

That line of text does not exist as a single, complete string, hence your failure to grep it.
This all gets rolling when free_initmem() in init/main.c calls free_initmem_default().

有问题的行源自 include/linux/mm.h 中的 free_initmem_default():

/*
 * Default method to free all the __init memory into the buddy system.
 * The freed pages will be poisoned with pattern "poison" if it's within
 * range [0, UCHAR_MAX].
 * Return pages freed into the buddy system.
 */
static inline unsigned long free_initmem_default(int poison)
{
    extern char __init_begin[], __init_end[];

    return free_reserved_area(&__init_begin, &__init_end,
                  poison, "unused kernel");
}

该文本的其余部分来自 mm/page_alloc.c 中的 free_reserved_area():

The rest of that text is from free_reserved_area() in mm/page_alloc.c:

unsigned long free_reserved_area(void *start, void *end, int poison, const char *s)
{
    void *pos;
    unsigned long pages = 0;

    ...

    if (pages && s)
        pr_info("Freeing %s memory: %ldK\n",
            s, pages << (PAGE_SHIFT - 10));

    return pages;
}

(v5.2中的代码摘录)

(Code excerpts from v5.2)

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