The page->_count is the page frame's usage count.

When page is allocated, the page will be refcounted, and page->_cout will be set 1.

After be allocated from buddy system, the page will be used by process.  get_page and put_page/put_page_testzero will used in pairs. is it right?

When the page is reclaimed to buddy system, the page->_count should be 0. However, Because the initialization of page->_count is 1, get_page() and put_page() is called in pairs, I coufused how page->_count will be 0?   

Thanks.