From owner-freebsd-net Thu Jul 11 16:20:31 2002 Delivered-To: freebsd-net@freebsd.org Received: from mx1.FreeBSD.org (mx1.FreeBSD.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 4CB9A37B400 for ; Thu, 11 Jul 2002 16:20:27 -0700 (PDT) Received: from rwcrmhc52.attbi.com (rwcrmhc52.attbi.com [216.148.227.88]) by mx1.FreeBSD.org (Postfix) with ESMTP id B306243E09 for ; Thu, 11 Jul 2002 16:20:26 -0700 (PDT) (envelope-from julian@elischer.org) Received: from InterJet.elischer.org ([12.232.206.8]) by rwcrmhc52.attbi.com (InterMail vM.4.01.03.27 201-229-121-127-20010626) with ESMTP id <20020711232026.CGQA8262.rwcrmhc52.attbi.com@InterJet.elischer.org>; Thu, 11 Jul 2002 23:20:26 +0000 Received: from localhost (localhost.elischer.org [127.0.0.1]) by InterJet.elischer.org (8.9.1a/8.9.1) with ESMTP id QAA48704; Thu, 11 Jul 2002 16:10:33 -0700 (PDT) Date: Thu, 11 Jul 2002 16:10:32 -0700 (PDT) From: Julian Elischer To: Bosko Milekic Cc: Luigi Rizzo , freebsd-net@FreeBSD.ORG Subject: Re: mbuf external buffer reference counters In-Reply-To: <20020711171255.A19014@unixdaemons.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-net@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org On Thu, 11 Jul 2002, Bosko Milekic wrote: > > Well, I can use a different map, I guess (I use a different map for > mbufs in order to not let huge cluster allocations eat up all of the > address space reserved for mbufs). However, it seems that jumbo bufs > and clusters are logically equivalent (your driver will either use one > or the other) so it would make sense to have them share the same > `chunk' of address space. > > As for the gaps, they are quite huge. I think we calculated a week or > so ago when discussing jumbo bufs that we would probably end up > allocating them in chunks of 3 or 4 at a time. So that would mean at > least ~9 page 'holes' in the address space from which clusters are > allocated, so that would mean ~18 counters wasted, at least, for every > hole. With the number of jumbo bufs we would have, that can really > add up. Don't forget that "external" does not neccesarily mean "cluster". I still consider the method used in (hmm was it NetBSD or OSF/1?) to be very good.. mbufs that referred to the same object were linked together. I forget the details exactly. maybe someone else can remember.. it did it without ref counts somehow.. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message