This crate implements a lightweight memory profiler which allows object traversal and memory size introspection.
Allocative trait (typically implemented with proc-macro) is introspectable:
Allocative values can be traversed and their size and sizes of referenced
objects can be collected.
This crate provides a few utilities to work with such objects, the main of such utilities is flame graph builder which produces flame graph (see the crate documentation) like this:
Allocative is not a substitute for call stack malloc profiler, it provides a different view of memory usage.
Here are some differences between allocative and call-stack malloc profiler:
- Allocative requires implementation of
Allocativetrait for each type which needs to be measured, and some setup in the program to enable it is needed - Allocative flamegraph shows object by object tree, not by call stack
- Allocative shows gaps in allocated memory, e.g. spare capacity of collections or too large padding in structs or enums
- Allocative allows profiling of non-malloc allocations (for example, allocations within bumpalo bumps)
- Allocative allows profiling of memory for subset of the process data (for example, measure the size of RPC response before serialization)
When allocative is used, binary size is slightly increased due to
implementations of [Allocative] trait, but it has no runtime/memory overhead
when it is enabled but not used.
Note there are several copies of this project on GitHub due to how Meta monorepo is synchronized to GitHub. The main copy is facebookexperimental/allocative.
Allocative is both MIT and Apache License, Version 2.0 licensed, as found in the LICENSE-MIT and LICENSE-APACHE files.