我试图理解进程的smaps文件中“Referenced”的含义。
根据内核文档：
“Referenced”表示当前标记为Referenced或
已访问。“
我理解“访问”的含义，但它是什么意思“引用”？
如果它都是访问的内存，那么我希望它是“RSS”+“Swap”，但是在下面的示例中，它不是这样的。
例子：
7f13e7577000-7f13e75c1000 rw-p 00000000 00:00 0 [heap]
Size: 296 kB
Rss: 156 kB
Pss: 156 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 4 kB
Private_Dirty: 152 kB
Referenced: 128 kB
Anonymous: 156 kB
AnonHugePages: 0 kB
Swap: 56 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Locked: 0 kB
最佳答案
从定义内存页标志位的Linux kernel source code，referenced，PG_referenced用于回收匿名、文件支持的页面缓存的页面。PG_reclaim标志位用于referenced中，进一步记录为，
/*
* All mapped pages start out with page table
* references from the instantiating fault, so we need
* to look twice if a mapped file page is used more
* than once.
*
* Mark it and spare it for another trip around the
* inactive list. Another page table reference will
* lead to its activation.
*
* Note: the mark is set for activated pages as well
* so that recently deactivated but used pages are
* quickly recovered.
*/
同时
page_check_references()是从Linux内核的不同地方调用的函数，它记录了在页面生命周期的初始部分对mark_page_accessed()标记位的更新：（即从新分配页面开始）
* Mark a page as having seen activity.
*
* inactive,unreferenced -> inactive,referenced
* inactive,referenced -> active,unreferenced
* active,unreferenced -> active,referenced
*
* When a newly allocated page is not yet visible, so safe for non-atomic ops,
* __SetPageReferenced(page) may be substituted for mark_page_accessed(page).
*/
即
referenced=近期不会回收的活动页缓存。