Re: [PATCH]: Adding a counter in vma to indicate the number of physical pages backing it

Rohit Seth
2006-06-12T17:49:46Z

On Fri, 2006-06-09 at 19:42 -0700, Andrew Morton wrote:
> On Fri, 09 Jun 2006 18:33:55 -0700
> Rohit Seth <rohitseth@google.com> wrote:
>
> > Below is a patch that adds number of physical pages that each vma is
> > using in a process. Exporting this information to user space
> > using /proc/<pid>/maps interface.
>
> Ouch, that's an awful lot of open-coded incs and decs. Isn't there some
> more centralised place we can do this?
>

I'll look into this. Possibly combining it with mm counters.

> What locking protects vma.nphys (can we call this nr_present or something?)
>

I'll need to use the same atomic counters as mm. And Yes nr_present is
a better name.

> Will this patch do the right thing with weird vmas such as the gate vma and
> mmaps of device memory, etc?
>

I think so. (though strictly speaking those special vmas are less
interesting). But final solution (if we do decide to implement this
counter) will address that.

-rohit