Re: [rfc] no ZERO_PAGE?

Nick Piggin
2007-04-05T02:30:26Z

On Wed, Apr 04, 2007 at 05:27:31PM -0700, Linus Torvalds wrote:
>
>
> On Wed, 4 Apr 2007, Valdis.Kletnieks@vt.edu wrote:
> >
> > I'd not be surprised if there's sparse-matrix code out there that wants to
> > malloc a *huge* array (like a 1025x1025 array of numbers) that then only
> > actually *writes* to several hundred locations, and relies on the fact that
> > all the untouched pages read back all-zeros.
>
> Good point. In fact, it doesn't need to be a malloc() - I remember people
> doing this with Fortran programs and just having an absolutely incredibly
> big BSS (with traditional Fortran, dymic memory allocations are just not
> done).

Sparse matrices are one thing I worry about. I don't know enough about
HPC code to know whether they will be a problem. I know there exist
data structures to optimise sparse matrix storage...