Re: Page fault scalability patch V18: Drop first acquisition of ptl

[Christoph Lameter]

On Thu, 3 Mar 2005, Andrew Morton wrote:

> Christoph Lameter <clameter@xxxxxxx> wrote:
> >
> > On Wed, 2 Mar 2005, Andrew Morton wrote:
> >
> >  > >  This is not relevant since it only deals with file pages.
> >  >
> >  > OK.   And CONFIG_DEBUG_PAGEALLOC?
> >
> >  Its a debug feature that can be fixed if its broken.
>
> It's broken.
>
> A fix would be to restore the get_page() if CONFIG_DEBUG_PAGEALLOC.  Not
> particularly glorious..

Another fix would be to have a global variable "dontunmap" and have
the map kernel function not change the pte. But this is also not the
cleanest way.

The problem with atomic operations is the difficulty of keeping state. The
state must essentially all be bound to the atomic value replaced otherwise
more extensive locking schemes are needed.


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