If I run an application which has shared library twice, almost double shared memory is consumed

[jaeseok-park]

Hi all.
I'm using Linux, however don't know well about shared memory and shared library concept.
I'd like to use ps_mem to calculate and analyze my application's memory usage but I got a question.

My application uses a big shared library. (.so files)
It's architecture is as below:

1. My application is composed of part A and B.
2. A is run as a process.
3. A forks B, so that B is run as another process.
4. A can forks B many times.
5. B uses a big shared library C.

Case 1: A forks B once.

 10.6 MiB + 614.5 KiB =  11.2 MiB       A
106.0 MiB +  28.5 MiB = 134.4 MiB       B

Case 2: A forks B twice.

 12.6 MiB + 432.5 KiB =  13.0 MiB       A
180.6 MiB +  59.3 MiB = 239.9 MiB       B (2)

Case 3: A forks B three times.

 14.6 MiB + 350.5 KiB =  15.0 MiB       A
270.5 MiB +  74.1 MiB = 344.6 MiB       B (3)

I thought that the big shared library, C might be shared, so that B's shared memory size might be almost same.
But, according to the test result, its size might be multiplied as the number of forks.

Why is the shared size multiplied?