On Wed, 4 Jul 2001, Stefan Seefeld wrote:
> there is no notion of 'physical memory' outside the kernel, at least
> not in anything remotely related to Unix.
> Why would you care about that anyway ? Whenever you do, you better
> put that stuff into a driver.
Well, there are benefits to being able to mlock memory, in that
the driver doesn't have to be the one to track ownership of locked-up
pages, plus that way the driver cannot be used to circumvent ulimits.
Still, you have to tell the driver about the memory in
any case if you want the driver to use it from kernel space, such
that the driver can find the kernelspace address, but at least
the driver isn't duplicating the functions of the kernel mm if the
userspace app can do the initial aquisition/freeing.
Anyway, we do not necessarily _always_ want to use a "real ram" allocation
with a graphics driver; could be useful to have a page that you
doodle on with no possibility of swap device delay, though I imagine
that will be of limited utility.
--
Brian
