This crate provides tools for measuring the heap memory usage of specific structures.
To measure your struct's memory usage, it and all of its child types must implement the MallocSizeOf trait.
For types that are local to your crate, this is really easy. Just add:
#[derive(MallocSizeOf)]For external types, you'll need to implement the trait here in external_impls.rs. See the existing implementations in that file for examples.
Note that size_of should return only the number of heap-allocated bytes used by the type. For example, a type such as struct MyStruct([u8; 128]) would return zero, not 128. Recursive accounting for heap-allocated memory when your struct is part of e.g. a Vec or HashMap is already taken care of by the implementations of MallocSizeOf on those collection types.
Oftentimes, the public interface of the type you are measuring does not provide enough information to precisely measure the amount of heap space it allocates. In that case, you can try just to produce a reasonable estimate.
To compute the heap usage of an annotated type at runtime, simply call mysten_util_mem::malloc_size(&my_struct). For complete memory usage, add in the inline size of the type as well, as in:
mysten_util_mem::malloc_size(&my_struct) + std::mem::size_of::<MyStruct>()For an example PR using library, take a look at https://github.com/MystenLabs/narwhal/pull/898/files.