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Date: Tue, 20 Feb 2007 12:30:18 +0100 From: Eric Dumazet <dada1@...mosbay.com> To: Evgeniy Polyakov <johnpol@....mipt.ru> Cc: David Miller <davem@...emloft.net>, akepner@....com, linux@...izon.com, netdev@...r.kernel.org, bcrl@...ck.org Subject: Re: Extensible hashing and RCU On Tuesday 20 February 2007 12:10, Eric Dumazet wrote: > > > Yep, it happend to be my tests :) > > Jenkins hash was slower and had significant artifacts for some usage > > cases ended up with extremely long chain length. > > One can find more details at > > http://tservice.net.ru/~s0mbre/blog/2006/05/14#2006_05_14 > > http://tservice.net.ru/~s0mbre/blog/2006/06/01#2006_06_01 > > Please explain why you chose h = jhash_2words(faddr, laddr, ports); > h ^= h >> 16; > h ^= h >> 8; > > jhash is very good, no need to try to be smarter, shufling some bytes... > and adding artifacts. I checked with my simulator and got no differences with the extra ops, at least no artifacts. Maybe this is related to the fact my hash size is 2^20 ? If we use jenkin hash: [0]:617469 0% [1]:326671 58.7654% [2]:86704 89.9601% [3]:15387 98.264% [4]:2103 99.7773% [5]:216 99.9716% [6]:24 99.9975% [7]:2 100% If we use jenkin hash (+plus Evgeniy Polyakov shifts) : [0]:617553 0% [1]:326403 58.7172% [2]:86902 89.9831% [3]:15462 98.3275% [4]:2012 99.7753% [5]:216 99.9696% [6]:27 99.9987% [7]:1 100% - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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