Date: Thu, 15 Feb 1996 00:18:49 -0800 From: David Greenman <davidg@Root.COM> To: Alan Cox <alc@cs.rice.edu> Cc: hackers@freebsd.org Subject: Re: VM question Message-ID: <199602150818.AAA06083@Root.COM> In-Reply-To: Your message of "Thu, 15 Feb 1996 01:39:46 CST." <199602150739.BAA16225@noel.cs.rice.edu>
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>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
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