[openib-general] Re: [PATCH][RFC][0/4] InfiniBand userspace verbs implementation

[Timur Tabi]

Roland Dreier wrote:

> Yes, I agree.  If an app wants to register half a page and pass the
> other half to a child process, I think the only answer is "don't do
> that then."

How can the app know that, though?  It would have to allocate I/O buffers with knowledge 
of page boundaries.  Today, the apps just malloc() a bunch of memory and pay no attention 
to whether the beginning or the end of the buffer shares a page with some other, unrelated 
object.  We may as well tell the app that it needs to page-align all I/O buffers.

My point is that we can't just simply say, "Don't do that".  Some entity (the kernel, 
libraries, whatever) should be able to tell the app that its usage of memory is going to 
break in some unpredictable way.

-- 
Timur Tabi
Staff Software Engineer
timur.tabi at ammasso.com

One thing a Southern boy will never say is,
"I don't think duct tape will fix it."
      -- Ed Smylie, NASA engineer for Apollo 13