Date: Tue, 14 Mar 1995 23:33:21 -0800 From: Steven Wallace <swallace@ece.uci.edu> To: terry@cs.weber.edu (Terry Lambert) Cc: current@FreeBSD.org Subject: Re: MINFREE change to 8% Message-ID: <199503150733.AA07893@balboa.eng.uci.edu> In-Reply-To: Your message of "Tue, 14 Mar 1995 16:42:23 MST." <9503142342.AA09959@cs.weber.edu>
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> You could probably do away with the reserve entirely (but killing the > ability to exercise administrative fiat in the process, it being a > side effect of the reserve) by moving from a vector hash to skiplists. > > The 10% is the 90% fill point for least acceptable performance on the > hash; anything over 90% is deemed unacceptable. The actual fall off > is expotential and starts sucking at 80-85% (Knuth). > > When you dick with the minfree, you are in fact lowering the bottom > watermark for acceptable performance for the system. It really doesn't > matter that you think you are "wasting" 100M on a 1G disk; what you > are paying for is a reduced average hash collision frequency. > > The only real difference on a 1G disk is that it become obvious that > you are tying up a lot of disk based on your choice of algorithms. > Could someone explain to the ignorant what in the world you are hashing? (you are searching for something and use some algorithm as your hash index into the 10% reserve space on the disk? (is this reserve distributed or continuous at a specific portion of the disk?) Then you find something... ?) How do skiplist compare and how would they be implemented? Steven
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