What is the concurrent mark-sweep generation in the heap?

In the following output, what is the concurrent mark-sweep generation?

par new generation   total 24512K, used 12082K [0x00007fb3b9420000, 0x00007fb3bac20000, 0x00007fb3bac20000)
 eden space 24448K,  49% used [0x00007fb3b9420000, 0x00007fb3b9fec808, 0x00007fb3bac0开发者_开发技巧0000)
 from space 64K,   0% used [0x00007fb3bac10000, 0x00007fb3bac10000, 0x00007fb3bac20000)
 to   space 64K,   0% used [0x00007fb3bac00000, 0x00007fb3bac00000, 0x00007fb3bac10000)
concurrent mark-sweep generation total 8364032K, used 233100K [0x00007fb3bac20000, 0x00007fb5b9420000, 0x00007fb5b9420000)
concurrent-mark-sweep perm gen total 98304K, used 72031K [0x00007fb5b9420000, 0x00007fb5bf420000, 0x00007fb5bf420000)

I understand eden, from, to and perm gen, but what is "concurrent mark-sweep generation"?

"concurent mark-sweep generation" is the old generation.

I don't think that a "concurent mark-sweep generation" exists as such. Concurrent Mark-Sweep refers to the Garbage Collection alogorithm that is being used, in this case, to collect against the "old" heap.

The heap is generally in 3 generations. Eden, From and To are in the new generation, the old generation contains long lived objects that have survivied a number of collection in "new" and have been tenured ( transferred to the "old" generation.) The Third generation is the permanent generation, which it looks like you already have an understanding of.