Android dumpsys meminfo "Swapped Dirty" coloumn meaning?

Question

There are many questions asked regarding output of the "adb shell dumpsys meminfo" like this one: adb shell dumpsys meminfo - What is the meaning of each cell of its output? And now we have this nice article describing types of memory allocations: https://developer.android.com/tools/debugging/debugging-memory.html

And yet, there is no mentioning of "Swapped Dirty" type of memory allocation. What is this beast? AFAIK, Android does not swap dirty pages and yet sometimes I'll get non zero value in that column:

                  Pss  Private  Private  Swapped     Heap     Heap     Heap
                Total    Dirty    Clean    Dirty     Size    Alloc     Free
               ------   ------   ------   ------   ------   ------   ------
 Native Heap     3861     3844        0     2024     7128     6801      326
 Dalvik Heap     7073     6996        0     5408    45111    31778    13333

Answer 1

Some Android devices do use swap, but they swap to RAM rather than flash. Linux has a feature called ZRAM that compressed pages and then swaps them to a special RAM area, and decompresses them again when needed.

So the pages listed in "Swapped Dirty" are likely in ZRAM.