From c430e326b9d0977538a4f4ff9059fd2e6e16d993 Mon Sep 17 00:00:00 2001
From: Florian Engelhardt <florian.engelhardt@datadoghq.com>
Date: Tue, 10 Mar 2026 11:18:57 +0100
Subject: [PATCH 1/2] Add benchmark for timestamped `add_sample`

---
 libdd-profiling/benches/add_samples.rs | 37 +++++++++++++++++++++-----
 1 file changed, 31 insertions(+), 6 deletions(-)

diff --git a/libdd-profiling/benches/add_samples.rs b/libdd-profiling/benches/add_samples.rs
index fc27d886b3..4edcd94dd1 100644
--- a/libdd-profiling/benches/add_samples.rs
+++ b/libdd-profiling/benches/add_samples.rs
@@ -106,12 +106,20 @@ pub fn bench_add_sample_vs_add2(c: &mut Criterion) {
     let functions = dict.functions();
     let thread_id = get_current_thread_id();
     let thread_id_key: StringId2 = strings.try_insert("thread id").unwrap().into();
-    let labels_api = vec![api::Label {
-        key: "thread id",
-        str: "",
-        num: thread_id,
-        num_unit: "",
-    }];
+    let labels_api = vec![
+        api::Label {
+            key: "thread id",
+            str: "",
+            num: thread_id,
+            num_unit: "",
+        },
+        api::Label {
+            key: "thread name",
+            str: "this thread",
+            num: 0,
+            num_unit: "",
+        },
+    ];
 
     let frames2 = frames.map(|f| {
         let set_id = functions
@@ -128,6 +136,23 @@ pub fn bench_add_sample_vs_add2(c: &mut Criterion) {
     });
     let dict = profiling::profiles::collections::Arc::try_new(dict).unwrap();
 
+    c.bench_function("profile_add_sample_timestamped_x1000", |b| {
+        b.iter(|| {
+            let mut profile = profiling::internal::Profile::try_new(&sample_types, None).unwrap();
+            let (locations, values) = make_stack_api(frames.as_slice());
+            for i in 0..1000 {
+                let sample = api::Sample {
+                    locations: locations.clone(),
+                    values: &values,
+                    labels: labels_api.clone(),
+                };
+                let ts = std::num::NonZeroI64::new(i + 1);
+                black_box(profile.try_add_sample(sample, ts)).unwrap();
+            }
+            black_box(profile.only_for_testing_num_aggregated_samples())
+        })
+    });
+
     c.bench_function("profile_add_sample_frames_x1000", |b| {
         b.iter(|| {
             let mut profile = profiling::internal::Profile::try_new(&sample_types, None).unwrap();

From 96fdc3bf6ae7ede2fee42a7317d9c33e3ab05941 Mon Sep 17 00:00:00 2001
From: Florian Engelhardt <florian.engelhardt@datadoghq.com>
Date: Tue, 10 Mar 2026 11:03:14 +0100
Subject: [PATCH 2/2] add `BufWriter` to limit calls to `ZSTD_compressStream`

---
 .../observation/timestamped_observations.rs    | 18 +++++++++++-------
 libdd-profiling/src/profiles/compressor.rs     | 10 ++++++++++
 2 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/libdd-profiling/src/internal/observation/timestamped_observations.rs b/libdd-profiling/src/internal/observation/timestamped_observations.rs
index b21219ff9f..69a0282442 100644
--- a/libdd-profiling/src/internal/observation/timestamped_observations.rs
+++ b/libdd-profiling/src/internal/observation/timestamped_observations.rs
@@ -12,12 +12,12 @@ use crate::collections::identifiable::Id;
 use crate::internal::Timestamp;
 use crate::profiles::{DefaultObservationCodec as DefaultCodec, ObservationCodec};
 use byteorder::{NativeEndian, ReadBytesExt};
-use std::io::{self, Write};
+use std::io::{self, BufWriter, Write};
 
 pub type TimestampedObservations = TimestampedObservationsImpl<DefaultCodec>;
 
 pub struct TimestampedObservationsImpl<C: ObservationCodec> {
-    compressed_timestamped_data: C::Encoder,
+    compressed_timestamped_data: BufWriter<C::Encoder>,
     sample_types_len: usize,
 }
 
@@ -40,10 +40,10 @@ impl<C: ObservationCodec> TimestampedObservationsImpl<C> {
 
     pub fn try_new(sample_types_len: usize) -> io::Result<Self> {
         Ok(Self {
-            compressed_timestamped_data: C::new_encoder(
-                Self::DEFAULT_BUFFER_SIZE,
-                Self::MAX_CAPACITY,
-            )?,
+            compressed_timestamped_data: BufWriter::with_capacity(
+                C::recommended_input_buf_size(),
+                C::new_encoder(Self::DEFAULT_BUFFER_SIZE, Self::MAX_CAPACITY)?,
+            ),
             sample_types_len,
         })
     }
@@ -74,8 +74,12 @@ impl<C: ObservationCodec> TimestampedObservationsImpl<C> {
     }
 
     pub fn try_into_iter(self) -> io::Result<TimestampedObservationsIterImpl<C>> {
+        let encoder = self
+            .compressed_timestamped_data
+            .into_inner()
+            .map_err(|e| e.into_error())?;
         Ok(TimestampedObservationsIterImpl {
-            decoder: C::encoder_into_decoder(self.compressed_timestamped_data)?,
+            decoder: C::encoder_into_decoder(encoder)?,
             sample_types_len: self.sample_types_len,
         })
     }
diff --git a/libdd-profiling/src/profiles/compressor.rs b/libdd-profiling/src/profiles/compressor.rs
index 6de02b8abd..83dc326d48 100644
--- a/libdd-profiling/src/profiles/compressor.rs
+++ b/libdd-profiling/src/profiles/compressor.rs
@@ -145,6 +145,12 @@ pub trait ObservationCodec {
 
     fn new_encoder(size_hint: usize, max_capacity: usize) -> io::Result<Self::Encoder>;
     fn encoder_into_decoder(encoder: Self::Encoder) -> io::Result<Self::Decoder>;
+
+    /// Returns the recommended input buffer size for the encoder.
+    /// Used to size the `BufWriter` that wraps the encoder.
+    fn recommended_input_buf_size() -> usize {
+        0
+    }
 }
 
 #[allow(unused)]
@@ -181,6 +187,10 @@ impl ObservationCodec for ZstdObservationCodec {
             Err((_enc, error)) => Err(error),
         }
     }
+
+    fn recommended_input_buf_size() -> usize {
+        zstd::Encoder::<SizeRestrictedBuffer>::recommended_input_size()
+    }
 }
 
 #[cfg(not(miri))]