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What is this?
We use jemalloc everywhere we can, for any binary that we expect to run in a long-lived process. The reason for this is that our workloads are:
- multi-threaded
- extremely prone to memory fragmentation (due to our heavy use of
serde_json, or json generally)
jemalloc helps reduce memory fragmentation hugely, to the point of solving production OOMs that would have made use of capture-rs for replay a non-starter with the default system allocator.
At time of writing (2024-09-04), rust workspaces don't have good support for specifying dependencies on a per-target basis, so this crate does the work of pulling in jemalloc only when compiling for supported targets, and then exposes a simple macro to use jemalloc as the global allocator. Anyone writing a binary crate should put this macro at the top of their main.rs. Libraries should not make use of this crate.
Future work
Functions could be added to this crate to, in situations where jemalloc is in use, report a set of metrics about the allocator, as well as other functionality (health/liveness, a way to specify hooks to execute when memory usage exceeds a certain threshold, etc). Right now, it's prety barebones.