[mkgmap-dev] Patch to reduce memory usage by interning strings.From Scott A Crosby scrosby at cs.rice.edu on Fri Apr 2 05:16:04 BST 2010
On Thu, 01 Apr 2010 12:10:22 +0100, Steve Ratcliffe <steve at parabola.me.uk> writes: > On 31/03/10 14:56, Scott A Crosby wrote: >> I noticed that mkgmap does not intern any strings. In particular, this > > This is true. There is a pending patch that deals with excessive > memory use in a slightly different way which is on the style-speed > branch, with a pre-built one available at the bottom of the mkgmap > download page. I pulled it out of SVN at 1569. > I drops all tags that are not used by the current style and as an > extra feature it ensures that there is only copy of all the strings > on the key side. > > Could you try it out please. It may be worth also interning the values > but when I was looking at it there was much less benefit for the maps > I was looking at (but it might vary with the input). > I'd be happy to apply a patch that interned the values too if there > was a decent memory saving without a significant performance drop. The style-speed branch builds the tile in question within 1gb of ram using the default style. I suspect that that style isn't using the problematic tags. A different style that did use the tags would likely still blow up. This seems fragile. I benchmarked the problematic tile on the style-speed branch with and without interning all keys and values in the Tag() constructor using ordinary String.intern(). The 18 character change implementing interning seems to increase performance by about a second, from 66 to 65 seconds. I'd say to go for it. Scott
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