If you consider that using least signifiant bits to store an
identifier of the address space is a bad idea, I'm open to discuss how
tracemalloc should be extended to support this use case.

--

malloc in POSIX standard:
http://pubs.opengroup.org/onlinepubs/009695399/functions/malloc.html
"The pointer returned if the allocation succeeds shall be suitably
aligned so that it may be assigned to a pointer to any type of object
and then used to access such an object in the space allocated (until
the space is explicitly freed or reallocated)."

Linux manual page has a simpler definition: "The malloc() and calloc()
functions return a pointer to the allocated memory, which is suitably
aligned for any built-in type."

malloc of the GNU libc:
"The address of a block returned by malloc or realloc in GNU systems
is always a multiple of eight (or sixteen on 64-bit systems)."
http://www.gnu.org/software/libc/manual/html_node/Aligned-Memory-Blocks.html

Random Google link for GPU:

"cudaMalloc() returns memory which is aligned at 256 bytes." (8 bits)
http://www.dmi.unict.it/~bilotta/gpgpu/notes/09-optimization.html

"Minimum alignment (bytes) for any datatype:    128"
http://unix.stackexchange.com/questions/187245/how-to-get-the-size-of-gpu-memory-available-for-opencl