Java - Collections.sort() performance

Question

I\'m using Collections.sort() to sort a LinkedList whose elements implements Comparable interface, so they are sorted in a natural order. In the javadoc documentation its sa

Answer 1

I am experimenting with large data sets (GBs of data) and have implemented a merge sort (there is a good example @ googlecode). However, I am using Collection.sort() to pre-sort my temporary buffers and in my experience Collection.sort() gets ridiculously slow at a certain threshold of data. With a auxiliary buffer of 96MB I can sort one of those buffers in about 30sec (note: this heavily depends on the comparators you use - I use a custom column layout with a quite complex column parser), however increasing this to a 128MB chunk size the time jumps to over 3 minutes. This is in no relation to the linear (or near linear) behavior I can observe for smaller chunks. This has so much impact, that a merge sort with smaller buffers in almost (?) all cases faster than a in memory sort using a 128MB buffer. To make this short: Merge sort is the way to go for large data sets beyond the 100MB boundary. I cannot really answer why that is, and those numbers might even be machine dependent (mine is a OS-X on a 2.6GHz i7 & 16GB memory).