Xmx and gc log max heap size difference?

Question

Need to know why there is difference between and 和之间存在差异
1563.749: [GC 1563.749: [ParNew: 226929K->11859K(235968K), 0.0605702 secs] 735329K->523980K( ), 0.0616580 secs] ），0.0616580秒]

Answer 1

-Xmx parameter specifies only the maximum heap size. JVM is free to choose any size lower than that and it could dynamically change. You could also specify initial heap size via -Xms and if you set it equal to -Xmx presumably heap size shouldn't change much.

UPDATE: Now when you mentioned that you also have -Xms == -Xmx my answer above no longer applies. Looking at your numbers again it appears that they're actually pretty close:

1,792M = 1,835,008K

So looks like the reported discrepancy is just about 27M or just slightly over 1%. Why is it concerning you?