On 4/5/18 5:44 PM, unDEFER wrote:
OK, without reallocation:
====================8<====================
void main()
{
float[3] f;
float[3][] x;
writefln("float = %s bytes", float.sizeof);
writefln("float[3] = %s bytes", f.sizeof);
int before = MemoryUsage();
int total = 100;
x = new float[3][total*1000];
int after = MemoryUsage();
writefln("%dK * float[3] = %d Kbytes", total, (after-before));
}
====================>8====================
$ ./memory
float = 4 bytes
float[3] = 12 bytes
100K * float[3] = 2300 Kbytes
Why this so?
1. Compare to C malloc-ing 1.2MB at once (GC uses C malloc underneath)
2. Have you examined smaller numbers for total? Does it scale linearly
or is there a threshold? (my guess is the latter)
Note that the GC does keep some metadata, but it's 1/32 the size of the
actual memory, so I'm not sure it's relevant here.
Is there an end goal for this exercise? That is, did you find a problem
and are trying to diagnose it by using this test? Maybe if we know the
real problem you are having, it can be explained differently.
-Steve
