I am interested whether should I manually inline small methods which are called 100k - 1 million times in some performance-sensitive algorithm.
First, I thought that, by not inlining, I am incurring some overhead since JVM will have to find determine whether or not to inline this method (or even fail to do so).
However, the other day, I replaced this manually inlined code with invocation of static methods and seen a performance boost. How is that possible? Does this suggest that there is actually no overhead and that by letting JVM inline at "its will" actually boosts performance? Or this hugely depends on the platform/architecture?
(The example in which a performance boost occurred was replacing array swapping (int t = a[i]; a[i] = a[j]; a[j] = t;) with a static method call swap(int[] a, int i, int j). Another example in which there was no performance difference was when I inlined a 10-liner method which was called 1000000 times.)