110 lines
4.1 KiB
Markdown
110 lines
4.1 KiB
Markdown
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:::{note}
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**AI Translation Notice**
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This document was automatically translated by `Qwen/Qwen3-8B` model, for reference only.
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- Source document: kernel/debug/profiling-kernel-with-dadk.md
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- Translation time: 2025-05-19 01:41:49
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- Translation model: `Qwen/Qwen3-8B`
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Please report issues via [Community Channel](https://github.com/DragonOS-Community/DragonOS/issues)
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:::
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# Performance Analysis of the Kernel Using DADK
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## 1. Overview
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This document will teach you how to use DADK to perform performance analysis on the DragonOS kernel, in order to identify and resolve potential performance bottlenecks.
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### 1.1 Preparation
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::: {note}
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Before you start, please ensure that you have installed DADK and have set up the compilation environment for the DragonOS kernel.
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:::
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### 1.2 What is a Flame Graph?
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If you haven't heard of flame graphs before, you can read this article: [How to Read Flame Graphs? - Ruanyifeng](https://www.ruanyifeng.com/blog/2017/09/flame-graph.html)
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In simple terms, a flame graph is an SVG image generated from performance sampling results, used to display the call stack of the CPU.
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The x-axis represents the number of samples. If a function occupies a wider width on the x-axis, it means it was sampled more frequently, indicating longer execution time. Note that the x-axis does not represent time, but rather all call stacks are merged and sorted alphabetically.
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A flame graph is used to identify which function at the top level occupies the largest width. If there is a "plateau" (flat area), it indicates that the function may have performance issues.
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Colors have no special meaning, as flame graphs represent the CPU's busy level, so warm tones are generally chosen.
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## 2. Configuring the DragonOS Kernel
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Since performance analysis requires detailed symbol table data, we need to configure the kernel compilation as follows:
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In `kernel/Cargo.toml`'s `[profile.release]` section, set the following two options:
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```toml
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[profile.release]
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debug = true
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opt-level = 1
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```
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This will ensure that the compiled kernel includes symbol table data, making it easier for us to perform performance analysis.
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## 3. Using DADK for Performance Analysis
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### 3.1 Booting the Kernel
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First, we need to boot the DragonOS kernel.
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```shell
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# 使用你喜欢的方式启动内核，例如：
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make run
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# 或者
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make build && make qemu-nographic
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```
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### 3.2 Running Your Workload
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After booting the kernel, we need to run some workloads in order to perform performance analysis.
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This can be an application or something else. Even you can choose to do nothing and simply observe the call stack of the DragonOS kernel when it is idle.
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### 3.3 Starting DADK for Performance Analysis
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In the DragonOS project directory, run the following command:
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```shell
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dadk profile sample --format flamegraph --output flame.svg --interval 200ms --duration 20s --cpu-mask 0x1
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```
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The above command will perform performance analysis on the DragonOS kernel and generate a flame graph.
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Detailed explanation:
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- `--format flamegraph`: Specifies the output format as a flame graph.
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- `--output flame.svg`: Specifies the output filename as `flame.svg`.
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- `--interval 200ms`: Specifies the sampling interval as 200ms.
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- `--duration 20s`: Specifies the sampling duration as 20 seconds.
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- `--cpu-mask 0x1`: Specifies the CPU to be sampled as CPU 0. (This is a bitmask, meaning if you want to sample CPU 0 and 1, the cpu-mask would be 0x3)
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*For more parameters, please refer to `dadk profile sample --help`.*
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::: {note}
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Since sampling will pause vCPU, the sampling time should not be too short, otherwise it may affect the normal operation of the system.
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:::
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After waiting for a while, you will get a `flame.svg` file.
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### 3.4 Analyzing the Flame Graph
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Open the `flame.svg` file in a browser, and you will see a flame graph.
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You can click on a function in the flame graph to view its call stack.
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**You can right-click the image below and open it in a new tab to experience the interactive effects.**
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