From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Brian F. G. Bidulock" Subject: Re: Question about tcp hash function tcp_hashfn() Date: Thu, 1 Jun 2006 01:11:25 -0600 Message-ID: <20060601011125.C22283@openss7.org> References: <20060531090301.GA26782@2ka.mipt.ru> <20060531035124.B3065@openss7.org> <20060531105814.GB7806@2ka.mipt.ru> <20060531.114127.14356069.davem@davemloft.net> <20060601060424.GA28087@2ka.mipt.ru> <20060601001825.A21730@openss7.org> <20060601063012.GC28087@2ka.mipt.ru> <20060601004608.C21730@openss7.org> <20060601070136.GA754@2ka.mipt.ru> Reply-To: bidulock@openss7.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: David Miller , draghuram@rocketmail.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org Return-path: Received: from gw.openss7.com ([142.179.199.224]:21652 "EHLO gw.openss7.com") by vger.kernel.org with ESMTP id S1750729AbWFAHL0 (ORCPT ); Thu, 1 Jun 2006 03:11:26 -0400 To: Evgeniy Polyakov Content-Disposition: inline In-Reply-To: <20060601070136.GA754@2ka.mipt.ru>; from johnpol@2ka.mipt.ru on Thu, Jun 01, 2006 at 11:01:36AM +0400 Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Evgeniy, On Thu, 01 Jun 2006, Evgeniy Polyakov wrote: > On Thu, Jun 01, 2006 at 12:46:08AM -0600, Brian F. G. Bidulock (bidulock@openss7.org) wrote: > > > Since pseudo-randomness affects both folded and not folded hash > > > distribution, it can not end up in different results. > > > > Yes it would, so to rule out pseudo-random effects the pseudo- > > random number generator must be removed. > > > > > > > > You are right that having test with 2^48 values is really interesting, > > > but it will take ages on my test machine :) > > > > Try a usable subset; no pseudo-random number generator. > > I've run it for 2^30 - the same result: folded and not folded Jenkins > hash behave the same and still both results produce exactly the same > artifacts compared to XOR hash. But not without the pseudo-random number generation... ? > > Btw, XOR hash, as completely stateless, can be used to show how > Linux pseudo-random generator works for given subset - it's average of > distribution is very good. But its distribution might auto-correlate with the Jenkins function. The only way to be sure is to remove the pseudo-random number generator. Just try incrementing from, say, 10.0.0.0:10000 up, resetting port number to 10000 at 16000, and just incrementing the IP address when the port number wraps, instead of pseudo-random, through 2^30 loops for both. If the same artifacts emerge, I give in. Can you show the same artifacts for jenkins_3word?