From e2088bc0eac69dce02eab1cdac1089ab31a03171 Mon Sep 17 00:00:00 2001
From: Utkarsh Umesan Pillai <66651184+utpilla@users.noreply.github.com>
Date: Wed, 4 Sep 2024 00:18:22 +0000
Subject: [PATCH] Update CHANGELOG

---
 opentelemetry-sdk/CHANGELOG.md | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/opentelemetry-sdk/CHANGELOG.md b/opentelemetry-sdk/CHANGELOG.md
index 2f44b29e7f..4cc03a2f07 100644
--- a/opentelemetry-sdk/CHANGELOG.md
+++ b/opentelemetry-sdk/CHANGELOG.md
@@ -2,6 +2,11 @@
 
 ## vNext
 
+- Perf improvements for all metric instruments (except `ExponentialHistogram`) that led to **faster metric updates** and **higher throughput** [#1740](https://github.com/open-telemetry/opentelemetry-rust/pull/1740):
+  - **Zero allocations when recording measurements**: Once a measurement for a given attribute combination is reported, the SDK would not allocate additional memory for subsquent measurements reported for the same combination.
+  - **Minimized thread contention**: Threads reporting measurements for the same instrument no longer contest for the same `Mutex`. The internal aggregation data structure now uses a combination of `RwLock` and atomics. Consequently, threads reporting measurements now only have to acquire a read lock.
+  - **Lock-free floating point updates**: Measurements reported for `f64` based metrics no longer need to acquire a `Mutex` to update the `f64` value. They use a CAS-based loop instead.
+
 - `opentelemetry_sdk::logs::record::LogRecord` and `opentelemetry_sdk::logs::record::TraceContext` derive from `PartialEq` to facilitate Unit Testing.
 - Fixed an issue causing a panic during shutdown when using the
   `TokioCurrentThread` in BatchExportProcessor for traces and logs.