From owner-freebsd-net Wed Aug 30 14:11:17 2000 Delivered-To: freebsd-net@freebsd.org Received: from field.videotron.net (field.videotron.net [205.151.222.108]) by hub.freebsd.org (Postfix) with ESMTP id C15AD37B424 for ; Wed, 30 Aug 2000 14:11:10 -0700 (PDT) Received: from modemcable136.203-201-24.mtl.mc.videotron.net ([24.201.203.136]) by field.videotron.net (Sun Internet Mail Server sims.3.5.1999.12.14.10.29.p8) with ESMTP id <0G04003AUIEYL7@field.videotron.net> for freebsd-net@FreeBSD.ORG; Wed, 30 Aug 2000 17:01:47 -0400 (EDT) Date: Wed, 30 Aug 2000 17:05:05 -0400 (EDT) From: Bosko Milekic Subject: Re: Proposal to clarify mbuf handling rules In-reply-to: <200008301833.LAA31594@bubba.whistle.com> X-Sender: bmilekic@jehovah.technokratis.com To: Archie Cobbs Cc: freebsd-net@FreeBSD.ORG Message-id: MIME-version: 1.0 Content-type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-net@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org On Wed, 30 Aug 2000, Archie Cobbs wrote: > It makes sense to put the info about the shared mbuf data into the > (single) union mext_descr that all the mbuf's point to. But why > not put ext_flags in there as well? Simply because we don't need it shared. And since we don't need it shared, then we don't need to waste another 4 bytes per M_EXT mbuf for it. > Also, why are "perms" and "refcnt" in the same union? It seems like > you will lose the "perms" information when you increase refcnt to 2, > leading to the same problem mentioned before (a shared mbuf data > region going from 2 -> 1 reference does not become writable again). Uhm, no. They are _not_ in the same union. They are in the same structure, which is a member of a union containing both that structure and a next_desc pointer for the union free list. Read the code right now in -CURRENT, look for mext_refcnt union format. > What is "next_desc" used for? How does that affect this? For the free list, used solely by the mext_refcnt (to be mext_descr) allocator. > -Archie > > ___________________________________________________________________________ > Archie Cobbs * Whistle Communications, Inc. * http://www.whistle.com Regards, Bosko Milekic bmilekic@technokratis.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message