[openib-general] Question about pinning memory

[Gleb Natapov]

On Mon, Jul 25, 2005 at 08:47:48AM -0700, Roland Dreier wrote:
>     Gleb> I think the better approach would be to send signal to
>     Gleb> process whenever vma list changes and let application verify
>     Gleb> whether cache entries should be freed.
> 
> It's probably better to use a file descriptor for kernel upcalls to
> userspace.  Then you don't have to go through the expensive signal
> delivery path.  Also you're not limited to the info you can squeeze
> into the siginfo.
Can you elaborate on kernel upcalls mechanism?

> 
> In this case I'm not sure whether it's better to have things driven by
> userspace or the kernel.  Having the kernel push new info up to
> userspace seems more efficient, since the kernel knows exactly when
> things have changed, but this seems to lead to synchronization
> problems where userspace may post a work request using an obsolete
> mapping before it gets the notification that the mapping changed.
>
This is responsibility of the user to make sure he is not unmaps or frees
memory that is currently in use.

--
			Gleb.