From owner-freebsd-arch Tue Jan 15 1:12:49 2002 Delivered-To: freebsd-arch@freebsd.org Received: from smtp.tninet.se (sheridan.tninet.se [195.100.94.102]) by hub.freebsd.org (Postfix) with ESMTP id B386537B402 for ; Tue, 15 Jan 2002 01:12:40 -0800 (PST) Received: from kairos.algonet.se (kairos.algonet.se [194.213.75.171]) by sheridan.tninet.se (BMR ErlangTM/OTP 3.0) with ESMTP id 865528.85957.1011.1s3624182sheridan for ; Tue, 15 Jan 2002 10:12:37 +0100 Received: (qmail 23323 invoked by uid 2493); 15 Jan 2002 09:12:35 -0000 Date: 15 Jan 2002 09:12:35 -0000 Message-ID: <20020115091235.23322.qmail@kairos.algonet.se> From: Mats Lofkvist To: tlambert2@mindspring.com Cc: imp@village.org, bmilekic@technokratis.com, arch@FreeBSD.ORG In-reply-to: <3C439B25.27DCCB2D@mindspring.com> (message from Terry Lambert on Mon, 14 Jan 2002 18:59:49 -0800) Subject: Re: 64 bit counters again References: <20020114105859.A24635@technokratis.com> <3C4305E5.65BB32A6@FreeBSD.org> <20020114114911.A24990@technokratis.com> <20020114.130705.84407599.imp@village.org> <3C439B25.27DCCB2D@mindspring.com> Sender: owner-freebsd-arch@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG From: Terry Lambert > > A 64-bit qauntity would take 738734374912 seconds to overflow if the > > 32-bit one overflowed in 172 seconds. That strikes me as a reasonable > > enough period of time. If I did the math right, that's on the order > > of 23 millinia (23425 years). > > Actually, it's closer to 4000 years, if the counter is for a > Gigabit Ethernet running a theoretical max wire speed, where a > 32 bit byte counter overflows in 32 seconds (1Gbit/S divided by 8 > to get bytes/S). > > Enough interfaces to saturate PCI-X drops this to 500 years (8Gbit/S). > > The Apple 802.11e FireWire wireless is already at 5Gbit. > > The idea that some counter size will never be exceeded by > technology by the time it is obsolete is what has people > complaining about 32 bit counters in this thread already; > are you prepared to make the same base assumption in the > choice of 64 bit counters? A terabit network could push > a 64 bit counter over in under 6 months. And it (a terabit network) would overflow the 1kB modular counter solution in 35 seconds or so. Yes, I know, larger blocks than 1kB should be used in the global counter, and I guess multiple levels of (32-bit) modular counters can be used to achieve higher limits, but will it still be cheaper than just using a 64 bit counter? _ Mats Lofkvist mal@algonet.se To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message