Re: [rfc] no ZERO_PAGE?

[Nick Piggin]

On Wed, Apr 04, 2007 at 05:27:31PM -0700, Linus Torvalds wrote:
> 
> 
> On Wed, 4 Apr 2007, Valdis.Kletnieks@xxxxxx 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...

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