From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 5 Apr 2007 04:30:26 +0200 From: Nick Piggin Subject: Re: [rfc] no ZERO_PAGE? Message-ID: <20070405023026.GE11192@wotan.suse.de> References: <20070329075805.GA6852@wotan.suse.de> <20070330024048.GG19407@wotan.suse.de> <20070404033726.GE18507@wotan.suse.de> <6701.1175724355@turing-police.cc.vt.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org Return-Path: To: Linus Torvalds Cc: Valdis.Kletnieks@vt.edu, Hugh Dickins , Andrew Morton , Linux Memory Management List , tee@sgi.com, holt@sgi.com, Andrea Arcangeli , Linux Kernel Mailing List List-ID: 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... -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org