What's the data in dalvik-LinearAlloc, dalvik-aux-structure, dalvik-bitmap-1, dalvik-bitmap-2, dalvik-card-table, dalvik-mark-stack and dalvik-zygote?

Question

I use showmap command on a PID, and I can't understand this part in the report:

 16384     3752      689        0     3132        0      620    4 /dev/ashmem/dalvik-LinearAlloc (deleted)
  2460     1748      934        0      828        0      920   18 /dev/ashmem/dalvik-aux-structure (deleted)
  8192      572      572        0        0        0      572    1 /dev/ashmem/dalvik-bitmap-1 (deleted)
  8192        0        0        0        0        0        0    1 /dev/ashmem/dalvik-bitmap-2 (deleted)
  4100      312      312        0        0        0      312    1 /dev/ashmem/dalvik-card-table (deleted)
502140    14860    14860        0        0        0    14860    3 /dev/ashmem/dalvik-heap (deleted)
  1500      280      280        0        0        0      280    1 /dev/ashmem/dalvik-jit-code-cache (deleted)
174764        0        0        0        0        0        0    1 /dev/ashmem/dalvik-mark-stack (deleted)
 22148    22148     2141        0    20452        0     1696    1 /dev/ashmem/dalvik-zygote (deleted)

I want to know what data is in the dalvik-LinearAlloc, dalvik-aux-structure, dalvik-bitmap-1, dalvik-bitmap-2, dalvik-card-table, dalvik-mark-stack and dalvik-zygote.

These ashmem cost millions bytes memory, and I want to find a measure to shrink the size of these ashmem.

Answer 1

showmap is dumpping the smap data from one process. The smap is describing the process's memory area's detail. In virtual memory manage system, the memory can be gained by the system API such as mmap, brk. After gaining virtual memory address by these APIs, the address and length will be recorded in the smap.

And let's list each section of the dalvik relative memory usage:

• Dalvik Heap section(Heap Management, GC)
  • dalvik-bitmap-1, dalvik-bitmap-2 is the Dalvik Heap management data stucture. In Dalvik, the GC is marksweep, and 8 bytes memory will be marked(Used or free) as one bit in the bitmap. These two bitmaps will be used as active map(used for marking @ runtime) and the other will be used as marked map(used @ GC time).
  • dalvik-mark-stack: For GC mark step use. The mark step will iterate the bitmap, so this is a Breadth-first search which will need a stack.
  • dalvik-card-table: is used for Dalvik Concurrent GC, in bitmap marking steps, the process will do other tasks which will lead using memory. These card tables is recording the memory dirty after first marking step. You can see the detail by searching mark sweep GC.
  • dalvik-heap is used for process memory usage
  • dalvik-zygote is one part of the hole heap, which will not be used @ GC. All processes will share these memories such as framework resources.
• dalvik-jit is The jit memory used in Dalvik. JIT: just in time, which will convert dex bytecode to machine code which can be executed by CPU.
• dalvik-LinearAlloc: is the dalvik's perm memory such as: Method, Class definition datas, thread stack datas. These memory can be setted READONLY after parsing the class definition.
• dalvik-aux-structure: auxillary data structures, which will compress the method/class/string const reference. These references will be used @ each dex file, but sum of these memory will cost a large memory. So Dalvik create a tmp memory to shared these references.

If you want to analysis your program's memory, I suggest you to use MAT in eclipse. And the native heap usage, you can use mmap to manage.