Re: 3rd version of R/W mmap_sem patch available

Andi Kleen
2001-03-20T16:33:49Z

On Tue, Mar 20, 2001 at 05:08:36PM +0100, Linus Torvalds wrote:
> > General comment: an expensive part of a pagefault
> > is zeroing the new page. It'd be nice if we could
> > drop the page_table_lock while doing the clear_user_page()
> > and, if possible, copy_user_page() functions. Very nice.
>
> I don't think it's worth it. We should have basically zero contention on
> this lock now, and adding complexity to try to release it sounds like a
> bad idea when the only way to make contention on it is (a) kswapd (only
> when paging stuff out) and (b) multiple threads (only when taking
> concurrent page faults).

Isn't (b) a rather common case in multi threaded applications ?

-Andi