Date: Wed, 30 Aug 2000 17:05:05 -0400 (EDT) From: Bosko Milekic <bmilekic@dsuper.net> To: Archie Cobbs <archie@whistle.com> Cc: freebsd-net@FreeBSD.ORG Subject: Re: Proposal to clarify mbuf handling rules Message-ID: <Pine.BSF.4.21.0008301656240.10773-100000@jehovah.technokratis.com> In-Reply-To: <200008301833.LAA31594@bubba.whistle.com>
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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
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