The incremental GC algorithm doesn't honor initial heap sizing information.

Running java -Xincgc -Xms40m -XX:+PrintGCDetails on any program that requires
garbage collection will show the problem; note the heap capacity information
hasn't changed in runs with and without -Xms

java -Xincgc -XX:+PrintGCDetails SpecApplication _213_javac
[Full GC [Train MSC: 0K->0K(64K), 0.0342019 secs] 401K->150K(2176K), 0.0346194 secs]
Caching Off Speed = 100
======= _213_javac Starting =======
Run 0 start. Total memory=2228224 free memory=2062216
Javac benchmark starting...
[GC [DefNew: 2047K->64K(2112K), 0.0514502 secs][Train: 411K->411K(512K), 0.0050486 secs] 2047K->475K(2624K), 0.0568282 secs]
[GC [DefNew: 2112K->64K(2112K), 0.0716870 secs][Train: 1242K->1242K(1344K), 0.0091424 secs] 2523K->1306K(3456K), 0.0810552 secs]
[GC [DefNew: 2111K->63K(2112K), 0.0798091 secs][Train: 2121K->2117K(2240K), 0.0084122 secs] 3354K->2181K(4352K), 0.0884661 secs]
[GC [DefNew: 2111K->64K(2112K), 0.0888833 secs][Train: 3019K->3022K(3136K), 0.0714135 secs] 4229K->3086K(5248K), 0.1605512 secs]

--------------------------------------------
java -Xms40m -Xincgc -XX:+PrintGCDetails SpecApplication _213_javac
[Full GC [Train MSC: 0K->0K(64K), 0.0336268 secs] 401K->150K(2176K), 0.0340333 secs]
Caching Off Speed = 100
======= _213_javac Starting =======
Run 0 start. Total memory=2228224 free memory=2062216
Javac benchmark starting...
[GC [DefNew: 2047K->64K(2112K), 0.0507739 secs][Train: 411K->411K(512K), 0.0051257 secs] 2047K->475K(2624K), 0.0562189 secs]
[GC [DefNew: 2112K->64K(2112K), 0.0683358 secs][Train: 1242K->1242K(1344K), 0.0095738 secs] 2523K->1306K(3456K), 0.0781310 secs]
[GC [DefNew: 2111K->63K(2112K), 0.0790054 secs][Train: 2121K->2117K(2240K), 0.0088924 secs] 3354K->2181K(4352K), 0.0881336 secs]
[GC [DefNew: 2111K->64K(2112K), 0.0869500 secs][Train: 3019K->3022K(3136K), 0.0731426 secs] 4229K->3086K(5248K), 0.1603422 secs]

---------------------------------------------

Here's what the default collector shows:

java -XX:+PrintGCDetails SpecApplication _213_javac
[Full GC [Tenured: 0K->150K(1408K), 0.0327379 secs] 401K->150K(3520K), 0.0331502 secs]
Caching Off Speed = 100
======= _213_javac Starting =======
Run 0 start. Total memory=3604480 free memory=3438472
Javac benchmark starting...
[GC [DefNew: 2047K->64K(2112K), 0.0395421 secs] 2198K->535K(3520K), 0.0397442 secs]
[GC [DefNew: 2111K->64K(2112K), 0.0528567 secs] 2583K->1369K(3520K), 0.0529803 secs]
[GC [DefNew: 2111K->63K(2112K), 0.0564717 secs][Tenured: 2183K->2247K(2304K), 0.1085401 secs] 3417K->2247K(4416K), 0.1653788 secs]
[GC [DefNew: 2047K->63K(2112K), 0.0505313 secs] 4295K->3143K(5864K), 0.0506532 secs]

----------------------------------------------------
java -Xms40m -XX:+PrintGCDetails SpecApplication _213_javac
[Full GC [Tenured: 0K->150K(36416K), 0.0329173 secs] 401K->150K(40832K), 0.0334224 secs]
Caching Off Speed = 100
======= _213_javac Starting =======
Run 0 start. Total memory=41877504 free memory=41711496
Javac benchmark starting...
[GC [DefNew: 4352K->127K(4480K), 0.0917313 secs] 4502K->1473K(40896K), 0.0919376 secs]
[GC [DefNew: 4479K->128K(4480K), 0.1245865 secs] 5825K->3374K(40896K), 0.1247421 secs]
[GC [DefNew: 4479K->128K(4480K), 0.1266840 secs] 7726K->5436K(40896K), 0.1268390 secs]
[GC [DefNew: 4479K->128K(4480K), 0.1408333 secs] 9788K->7502K(40896K), 0.1409816 secs]