On Saturday, 2 December 2023 at 19:13:18 UTC, Vino B wrote:
Hi All,
Request your help in understanding the below program, with
the below program I can allocate 8589934592(8GB) it prints the
length 8589934592(8GB) where as my laptop has only 4 GB so the
confusion is that how can this program allocate 8GB RAM when I
have only 4GB of RAM installed
```
import std.algorithm.comparison : max;
import
std.experimental.allocator.building_blocks.allocator_list :
AllocatorList;
import std.experimental.allocator.building_blocks.bucketizer;
import std.experimental.allocator.building_blocks.free_list :
FreeList;
import std.experimental.allocator.building_blocks.region :
Region;
import std.experimental.allocator.building_blocks.segregator;
import std.experimental.allocator.common : unbounded;
import std.experimental.allocator.mallocator : Mallocator;
import std.stdio: writeln;
void main () {
alias FList = FreeList!(Mallocator, 0, unbounded);
alias A = Segregator!(
8, FreeList!(Mallocator, 0, 8),
128, Bucketizer!(FList, 1, 128, 16),
256, Bucketizer!(FList, 129, 256, 32),
512, Bucketizer!(FList, 257, 512, 64),
1024, Bucketizer!(FList, 513, 1024, 128),
2048, Bucketizer!(FList, 1025, 2048, 256),
3584, Bucketizer!(FList, 2049, 3584, 512),
4097 * 1024, AllocatorList!(n => Region!Mallocator(max(n,
1024 * 4096))),
Mallocator
);
A tuMalloc;
auto c = tuMalloc.allocate(8589934592); // 8GB
writeln(c.length); // output: 8589934592
tuMalloc.deallocate(c);
}
```
From,
Vino
This is normal behavior on linux, it's called overcommit memory,
i think it was meant to allow things like fork() to work properly
https://stackoverflow.com/a/7504354
