mark_page_accessed

mark_page_accessed() is the function that detects the working set
/*
 * Mark a page as having seen activity.
 *
 * If it was already so marked, move it
 * to the active queue and drop the referenced
 * bit. Otherwise, just mark it for future
 * action..
 */
void mark_page_accessed(struct page *page)
{
 	if (!PageActive(page) && PageReferenced(page)) {
 		activate_page(page);
 		ClearPageReferenced(page);
 		return;
 	}

 	/* Mark the page referenced, AFTER checking for previous usage.. */
 	SetPageReferenced(page);
}