Date: Thu, 11 Jul 2002 22:27:25 -0400 From: Bosko Milekic <bmilekic@unixdaemons.com> To: Julian Elischer <julian@elischer.org> Cc: Luigi Rizzo <rizzo@icir.org>, freebsd-net@FreeBSD.ORG Subject: Re: mbuf external buffer reference counters Message-ID: <20020711222725.A5284@unixdaemons.com> In-Reply-To: <Pine.BSF.4.21.0207111606440.47612-100000@InterJet.elischer.org>; from julian@elischer.org on Thu, Jul 11, 2002 at 04:10:32PM -0700 References: <20020711171255.A19014@unixdaemons.com> <Pine.BSF.4.21.0207111606440.47612-100000@InterJet.elischer.org>
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On Thu, Jul 11, 2002 at 04:10:32PM -0700, Julian Elischer wrote: > 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.. Yes, this is in NetBSD still and it is very elegant. I remember looking at this a long time ago but to be honest, the reason I didn't implement it then first escaped me. However, thanks to David Malone's awesome commit messages, I found it: rev 1.53 of sys/sys/mbuf.h, extract: [...] "NetBSD's system of linked lists of mbufs was cosidered, but Alfred felt it would have locking issues when the kernel was made more SMP friendly." [...] I think it's almost clear now that there are, in fact, no SMP issues with it (we don't do per-cluster locking, or anything ridiculous like that), so unless Alfred has the reason again, I'll consider that method again instead. Thanks for the constructive feedback. Regards, -- Bosko Milekic bmilekic@unixdaemons.com bmilekic@FreeBSD.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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