From owner-freebsd-hackers Thu Feb 15 00:18:49 1996 Return-Path: owner-hackers Received: (from root@localhost) by freefall.freebsd.org (8.7.3/8.7.3) id AAA19567 for hackers-outgoing; Thu, 15 Feb 1996 00:18:49 -0800 (PST) Received: from Root.COM (implode.Root.COM [198.145.90.17]) by freefall.freebsd.org (8.7.3/8.7.3) with SMTP id AAA19558 for ; Thu, 15 Feb 1996 00:18:45 -0800 (PST) Received: from localhost (localhost [127.0.0.1]) by Root.COM (8.6.12/8.6.5) with SMTP id AAA06083; Thu, 15 Feb 1996 00:18:50 -0800 Message-Id: <199602150818.AAA06083@Root.COM> X-Authentication-Warning: implode.Root.COM: Host localhost didn't use HELO protocol To: Alan Cox cc: hackers@freebsd.org Subject: Re: VM question In-reply-to: Your message of "Thu, 15 Feb 1996 01:39:46 CST." <199602150739.BAA16225@noel.cs.rice.edu> From: David Greenman Reply-To: davidg@Root.COM Date: Thu, 15 Feb 1996 00:18:49 -0800 Sender: owner-hackers@freebsd.org Precedence: bulk >in fact, it's a write. However, that's not the worst problem. All >of the VM systems derived from Mach/OSF (except DEC UNIX) have a severe >performance problem when you start mprotect'ing thousands of pages >individually. The vm map list eventually has one entry per page. >Consequently, sigbus and mprotect take forever, because the underlying >mechanisms search the vm map list. (The hint kept in the vm map >actually doesn't help much.) > >My group is fairly serious about using FreeBSD for our research (and >publishing results based on it). So I'd love to discuss this in more >detail with the developers responsible for the VM system. I believe that >coallescing adjacent vm map entries (where possible) would solve 90% >of the problem for us. That's interesting and something John or me will certainly look into! -DG David Greenman Core Team/Principal Architect, The FreeBSD Project