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From Jason Rennie <>
Subject Re: Taste and -XX:+NewRatio
Date Thu, 12 Nov 2009 22:24:06 GMT
Note, especially, that there is no override for amd64, which is
the architecture you are likely using if you have 4+ gigs of ram, so you're
stuck with the idiotic value of 2 unless you set the option explicitly.
 I.e. if you set a 1 gig heap, only 683m of that can be used for "old"
allocation.  And, for doing this kind of work, just about all your data is
"old", so your max heap needs to be set about 50% higher than what you
actually need (unless you set NewRatio to a sane value).  Any value between
8 and 12 should be fine for mahout as these are in the right ballpark and
aren't very different from a practical perspective (8 corresponds to 11%
new; 12 corresponds to 7.7% new).

More grumblings on java gc/memory:



Jason Rennie
Research Scientist, ITA Software

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