Strange memory usage

[ConsoleC137]

• I have looked for existing issues (including closed) about this

Bug Report

Version

axum v0.7.4
axum-core v0.4.3

Platform

Linux [..] 6.7.2-arch1-2 #1 SMP PREEMPT_DYNAMIC Wed, 31 Jan 2024 09:22:15 +0000 x86_64 GNU/Linux

Crates

axum = "0.7.4"
tokio = { version = "1.36.0", features = ["full"] }

Description

simplescreenrecorder-2024-02-07_03.49.11.webm
Greetings, everyone.
While testing axum, I noticed a strange feature: every time I ran wrk, the memory consumption increased. In the video above, each server outputs "Hello, World!". As you can see axum's memory consumption is increasing, while actix-web behaves quite predictably. I also tried adding an asynchronous wait to emulate an I/O operation, but this had no effect on memory consumption. At first I thought it looked like a memory leak, but I didn't jump to conclusions and continued testing. I noticed one detail: axum returns memory, but in my case it happened only after a few hours. I'm afraid that in production the application might crash with an OOM error.

My code:

use axum::{response::Html, routing::get, Router};

#[tokio::main]
async fn main() {
    let app = Router::new().route("/", get(handler));

    let listener = tokio::net::TcpListener::bind("127.0.0.1:3000")
        .await
        .unwrap();
    println!("listening on {}", listener.local_addr().unwrap());
    axum::serve(listener, app).await.unwrap();
}

async fn handler() -> Html<&'static str> {
    // optional
    tokio::time::sleep(std::time::Duration::from_millis(50)).await;

    Html("<h1>Hello, World!</h1>")
}

Please let me know if I have made any errors in the design of the Bug Report.

[Kav91]

Started noticing this as well, memory increasing by ~100-200kb per request.
Very similar behavior as mentioned here: #1546