check dirty page on linux

1. top ->'f' ->'v'

http://www.linuxforums.org/articles/using-top-more-efficiently_89.html.

Note: On 2.6.x, this field is always zero without unknown reason.

2.you can check the size of dirty pages by checking /proc/<pid>/smaps

http://www.linux.com/learn/tutorials/42048-uncover-the-meaning-of-tops-statistics