Date: Wed, 13 Dec 2000 16:03:03 -0700 From: Warner Losh <imp@village.org> To: Tony Finch <dot@dotat.at> Cc: Dag-Erling Smorgrav <des@ofug.org>, Gustavo Vieira Goncalves Coelho Rios <gustavo@ifour.com.br>, hackers@FreeBSD.ORG Subject: Re: very big mail spool directory Message-ID: <200012132303.QAA42413@harmony.village.org> In-Reply-To: Your message of "Wed, 13 Dec 2000 21:44:04 GMT." <20001213214404.P71002@hand.dotat.at> References: <20001213214404.P71002@hand.dotat.at> <3A368F8C.1918684F@ifour.com.br> <xzpsnns4jvx.fsf@flood.ping.uio.no>
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In message <20001213214404.P71002@hand.dotat.at> Tony Finch writes: : Dag-Erling Smorgrav <des@ofug.org> wrote: : > : >If you only have half a million users, pick a prime number K close to : >the square root of the expected number of users (724 in your case - : >closest primes are 719 and 727), create that many bucket directories, : >and place each user in bucket ID mod K. : : Why a prime number? All you need is an even spread, and given that : user IDs are usually allocated sequentially any modulus will do. Because Knuth has shown that prime numbers give the best spread in hash lookup tables. Warner To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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