I did some more experiments and that's the most I can get from the script, no matter how much free memory there is on the machine. Adding ./pharo --memory 2000m ... has no effect. [PhilMac:~/Documents/Smalltalk/2-MyWorkspaces/workspaceMemTest philippeback$] ./pharo Pharo.image memtest.st 501 1024000 memtest.st uptime 0h0m0s memory 25,004,444 bytes old 19,213,688 bytes (76.80000000000001%) young 5,384 bytes (0.0%) used 19,219,072 bytes (76.9%) free 5,785,372 bytes (23.1%) GCs 5 (62ms between GCs) full 1 totalling 76ms (24.5% uptime), avg 76.0ms incr 4 totalling 10ms (3.2% uptime), avg 2.5ms tenures 0 allocating: 501 times 1024000 bytes allocated: 513.02 MB time to run 0:00:00:06.27 3 times GC time to run 0:00:00:00.494 uptime 0h0m7s memory 534,974,360 bytes old 532,256,456 bytes (99.5%) young 7,092 bytes (0.0%) used 532,263,548 bytes (99.5%) free 2,710,812 bytes (0.5%) GCs 344 (21ms between GCs) full 87 totalling 5,822ms (82.2% uptime), avg 66.9ms incr 257 totalling 659ms (9.3% uptime), avg 2.6ms tenures 0 Since last view 339 (20ms between GCs) uptime 6.800000000000001s full 86 totalling 5,746ms (84.9% uptime), avg 66.8ms incr 253 totalling 649ms (9.600000000000001% uptime), avg 2.6ms tenures 0