[mkgmap-dev] splitter r261: performance improvements

Sun Dec 16 15:51:59 GMT 2012

Hi,

I've committed r261: Changes
-improve throughput:
 + use BufferedInputStream with 4MB buffer for pbf and o5m input
 + reduced (oversized) o5m writer hashtable (saves around 635KB for each
open output file),
 + improved hash function to avoid collisions
 + avoid GC because of obsolete new String()

On my machine, the effect is great:
When splitting germany.o5m with r260, the hard disk is rattling and
rattling, and it takes
between 75 and 110 secs to split the file (yes, very random results)
With r261, the disk sound is normal again and it takes more less 
constantly 60 secs to split the same file with the same parms.

I did some other tests regarding performance and found out that
splitter works best when input file is on a different disk (even a slow 
USB 2.0 drive) and heap (-Xmx) is big enough to avoid massive GC. 
It has no positive effect if you specify -Xmx7000m when -Xmx1600m is
already good enough.

Ciao,
Gerd

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