From: Chuck Lever Subject: Re: Re: An interesting performance thing ? Date: Wed, 14 Dec 2005 16:59:42 -0800 Message-ID: <43A0BFFE.2050906@citi.umich.edu> References: <00b901c600db$5d374960$1500000a@americas.hpqcorp.net> <17312.39940.985507.704832@cse.unsw.edu.au> <43A0A0D5.4040804@citi.umich.edu> <018401c60108$c9477f30$1500000a@americas.hpqcorp.net> <17312.45710.867019.969182@cse.unsw.edu.au> <43A0BC49.3070604@citi.umich.edu> <17312.49024.378295.414582@cse.unsw.edu.au> Reply-To: cel@citi.umich.edu Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------080801060009050006060005" Cc: Iozone , wli@holomorphy.com, nfs@lists.sourceforge.net Return-path: Received: from sc8-sf-mx1-b.sourceforge.net ([10.3.1.91] helo=mail.sourceforge.net) by sc8-sf-list2.sourceforge.net with esmtp (Exim 4.30) id 1EmhTJ-0000YE-PT for nfs@lists.sourceforge.net; Wed, 14 Dec 2005 16:59:49 -0800 Received: from citi.umich.edu ([141.211.133.111]) by mail.sourceforge.net with esmtps (TLSv1:AES256-SHA:256) (Exim 4.44) id 1EmhTI-00087r-JW for nfs@lists.sourceforge.net; Wed, 14 Dec 2005 16:59:50 -0800 To: Neil Brown In-Reply-To: <17312.49024.378295.414582@cse.unsw.edu.au> Sender: nfs-admin@lists.sourceforge.net Errors-To: nfs-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: Discussion of NFS under Linux development, interoperability, and testing. List-Post: List-Help: List-Subscribe: , List-Archive: This is a multi-part message in MIME format. --------------080801060009050006060005 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Neil Brown wrote: > A good question is: Do we ever need more than 4 bytes of hash > value? > We wouldn't for hash tables, but they may well be other uses of > hashes. > > If we don't then a function that maps and arbitrary mem buffer into > a u32 would be suitable general for all uses or all architectures, > though some special cases like 4byte and 8byte inputs could probably > be optimised sensibly. > > I suspect the function given in > http://burtleburtle.net/bob/hash/evahash.html > > my really be a good choice. > It does about 40 add/subtracts for each 4bytes, but seems to have good > properties. > (Hmm.. that is probably similar to a constant 32bit multiply, but > maybe the current code with a better non-sparse prime is just as > good). i haven't looked at how the network layer handles this issue, but it might be a good start if there is something there to reuse. --------------080801060009050006060005 Content-Type: text/x-vcard; charset=utf-8; name="cel.vcf" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="cel.vcf" begin:vcard fn:Chuck Lever n:Lever;Charles org:Network Appliance, Incorporated;Open Source NFS Client Development adr:535 West William Street, Suite 3100;;Center for Information Technology Integration;Ann Arbor;MI;48103-4943;USA email;internet:cel@citi.umich.edu title:Member of Technical Staff tel;work:+1 734 763-4415 tel;fax:+1 734 763 4434 tel;home:+1 734 668-1089 x-mozilla-html:FALSE url:http://troy.citi.umich.edu/u/cel/ version:2.1 end:vcard --------------080801060009050006060005-- ------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Do you grep through log files for problems? Stop! Download the new AJAX search engine that makes searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! http://ads.osdn.com/?ad_id=7637&alloc_id=16865&op=click _______________________________________________ NFS maillist - NFS@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/nfs