On 08/02/2010 07:01 PM, Shirley Ma wrote:

Hello Avi,

On Sun, 2010-08-01 at 11:18 +0300, Avi Kivity wrote:

quoted

I don't understand.  Under what conditions do you use
get_user_pages()
instead of get_user_pages_fast()?  Why?

The code always calls get_user_pages_fast, however, the page will be
unpinned in skb_free if the same page is not used again for a new
buffer. The reason for unpin the page is we don't want to pin all of the
guest kernel memory(memory over commit).

That is fine.

So get_user_pages_fast will
call slow path get_user_pages.

I don't understand this. gup_fast() only calls gup() if the page is 
swapped out or read-only.

Your previous comment is suggesting to keep the page pinned for
get_user_pages_fast fast path?

Right now I'm not sure I understand what's happening.

-- 
error compiling committee.c: too many arguments to function