From owner-freebsd-arch Fri Jan 31 16:49:27 2003 Delivered-To: freebsd-arch@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id A362137B401 for ; Fri, 31 Jan 2003 16:49:26 -0800 (PST) Received: from stork.mail.pas.earthlink.net (stork.mail.pas.earthlink.net [207.217.120.188]) by mx1.FreeBSD.org (Postfix) with ESMTP id 3B39343E4A for ; Fri, 31 Jan 2003 16:49:26 -0800 (PST) (envelope-from tlambert2@mindspring.com) Received: from pool0203.cvx21-bradley.dialup.earthlink.net ([209.179.192.203] helo=mindspring.com) by stork.mail.pas.earthlink.net with asmtp (SSLv3:RC4-MD5:128) (Exim 3.33 #1) id 18elq9-0000ZZ-00; Fri, 31 Jan 2003 16:49:02 -0800 Message-ID: <3E3B1928.384F8C42@mindspring.com> Date: Fri, 31 Jan 2003 16:47:36 -0800 From: Terry Lambert X-Mailer: Mozilla 4.79 [en] (Win98; U) X-Accept-Language: en MIME-Version: 1.0 To: Peter Wemm Cc: Gary Thorpe , "Andrew R. Reiter" , Julian Elischer , David Schultz , Scott Long , arch@FreeBSD.ORG Subject: Re: PAE (was Re: bus_dmamem_alloc_size()) References: <20030131184326.D70A42A89E@canning.wemm.org> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-ELNK-Trace: b1a02af9316fbb217a47c185c03b154d40683398e744b8a4fa5be0a4ef094526822fbedd8f675bc7350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c Sender: owner-freebsd-arch@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG Peter Wemm wrote: > Gary Thorpe wrote: > > Would this be part of a unified buffer-cache scheme though? If I have > > been following correctly, this memory cannot be directly mapped into > > processes address space (i.e. a process in one "segment" cannot access > > directly memory in another "segment"), so how would it be useful as a > > cache? Wouldn't this need lots of data copying as in bounce buffers? > > It the nasty PSE36 hack that cant be used for this. PAE works fine as > cache since it is all available to all processes. What Peter said: the thing you don't get is the ability to have more than 4G of KVA + UVA space, unless you split the VM and buffer cache. Also what Peter said about the performance penalty that comes from PAE, and what I said about the reliability penalty from #ifdef'ing and seperately maintaining the code side-by-side. -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message