From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [rfc] no ZERO_PAGE? In-Reply-To: Your message of "Wed, 04 Apr 2007 22:37:29 PDT." <20070405053729.GQ2986@holomorphy.com> From: Valdis.Kletnieks@vt.edu References: <20070329075805.GA6852@wotan.suse.de> <20070330024048.GG19407@wotan.suse.de> <20070404033726.GE18507@wotan.suse.de> <6701.1175724355@turing-police.cc.vt.edu> <20070405023026.GE11192@wotan.suse.de> <20070405053729.GQ2986@holomorphy.com> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="==_Exmh_1175793784_3378P"; micalg=pgp-sha1; protocol="application/pgp-signature" Content-Transfer-Encoding: 7bit Date: Thu, 05 Apr 2007 13:23:04 -0400 Message-ID: <8350.1175793784@turing-police.cc.vt.edu> Sender: owner-linux-mm@kvack.org Return-Path: To: William Lee Irwin III Cc: Nick Piggin , Linus Torvalds , Hugh Dickins , Andrew Morton , Linux Memory Management List , tee@sgi.com, holt@sgi.com, Andrea Arcangeli , Linux Kernel Mailing List List-ID: --==_Exmh_1175793784_3378P Content-Type: text/plain; charset=us-ascii On Wed, 04 Apr 2007 22:37:29 PDT, William Lee Irwin III said: > The actual phenomenon of concern here is dense matrix code with sparse > matrix inputs. The matrices will typically not be vast but may span 1MB > or so of RAM (1024x1024 is 1M*sizeof(double), and various dense matrix > algorithms target ca. 300x300). Most of the time this will arise from > the use of dense matrix code as black box solvers called as a library > by programs not terribly concerned about efficiency until something > gets explosively inefficient (and maybe not even then), or otherwise > numerically naive programs. This, however, is arguably the majority of > the usage cases by end-user invocations, so beware, though not too much. Amen, brother! :) At least in my environment, the vast majority of matrix code is actually run by graduate students under the direction of whatever professor is the Principal Investigator on the grant. As a rule, you can expect the grad student to know about rounding errors and convergence issues and similar program *correctness* factors. But it's the rare one that has much interest in program *efficiency*. If it takes 2 days to run, that's 2 days they can go get another few pages of thesis written while they wait. :) The code that gets on our SystemX (a top-50 supercomputer still) is usually well-tweaked for efficiency. However, that's just one system - there's on the order of several hundred smaller compute clusters and boxen and SGI-en on campus where "protect the system from cargo-cult programming by grad students" is a valid kernel goal. ;) --==_Exmh_1175793784_3378P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (GNU/Linux) Comment: Exmh version 2.5 07/13/2001 iD8DBQFGFTB4cC3lWbTT17ARAr4QAKCUI4s8HRIM5JThdIF9raNWVNBJYwCgsJaQ P4H7Ye4Ub7tMpNeaEfEZyTc= =QCOW -----END PGP SIGNATURE----- --==_Exmh_1175793784_3378P-- -- 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