Date: Wed, 30 Aug 2000 14:51:57 -0700 (PDT) From: Archie Cobbs <archie@whistle.com> To: Bosko Milekic <bmilekic@dsuper.net> Cc: freebsd-net@FreeBSD.ORG Subject: Re: Proposal to clarify mbuf handling rules Message-ID: <200008302151.OAA33212@bubba.whistle.com> In-Reply-To: <Pine.BSF.4.21.0008301656240.10773-100000@jehovah.technokratis.com> "from Bosko Milekic at Aug 30, 2000 05:05:05 pm"
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Bosko Milekic writes: > > 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. OK, that makes more sense... I misread it before. > > 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. OK.. so, no effect. So.. this all sounds good to me now. -Archie ___________________________________________________________________________ Archie Cobbs * Whistle Communications, Inc. * http://www.whistle.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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