I/O Latency Measurement eBPF Program

Overview

This demo is to monitor and measure the latency of block I/O requests in Linux systems, and output a histogram of I/O requests latencies.

The output histogram is printed regularly, and the interval between each print is determined by user.

     usecs               : count    distribution
         0 -> 1          : 0        |                                        |
         2 -> 3          : 0        |                                        |
         4 -> 7          : 0        |                                        |
         8 -> 15         : 0        |                                        |
        16 -> 31         : 0        |                                        |
        32 -> 63         : 0        |                                        |
        64 -> 127        : 1        |***                                     |
       128 -> 255        : 1        |***                                     |
       256 -> 511        : 5        |****************                        |
       512 -> 1023       : 2        |******                                  |
      1024 -> 2047       : 12       |****************************************|
      2048 -> 4095       : 6        |********************                    |
      4096 -> 8191       : 6        |********************                    |

Features

• Latency Measurement: Capture the latency of block I/O requests in microseconds.
• Histogram Display: Present latency distribution in a histogram for easy analysis.
• Low Overhead: Designed to minimize impact on system performance while providing accurate latency metrics.
• Dynamic Tracing: No need to modify or recompile the kernel to deploy iolatency(we are using ebpf so of course..)

Testing environment

This program was tested under the following environment:

• Operating System: Debian GNU/Linux
• Kernel Version: 6.1.0-13-amd64
• Architecture: x86_64

Prerequisites

• Kernel Version: 4.9 or newer with eBPF support enabled.
• LLVM/Clang: Version 6.0 or newer for compiling the eBPF program.
• libbpf: Required for the user space program to interact with eBPF.
• Root Access: Required for loading eBPF programs into the kernel.

Installation

Clone the Repository make

make

and run with sudo.

sudo ./iolatency n

n refers to the interval between printing histograms.

Testing Overview

The testing results are in ./test_output.

Below, you will find detailed instructions on how to execute the tests, along with a brief description of each component involved in the testing process.

• test.fio

This is a test fio configuration file to generate intensive I/O requests. Run by

  fio test.fio

• reference.sh

This is a reference script available under the GNU General Public License (http://www.gnu.org/copyleft/gpl.html). It also measures I/O request latencies and presents the results in a histogram format for easy analysis.

Comparative Testing

The performance was tested following these steps.

1. Execute both reference.sh and the iolatency tool in parallel.
2. While these tools are running, start the test.fio to generate I/O requests.
3. Record the output of reference.sh in reference_results.txt.
4. Similarly, capture the output of iolatency in iolatency_results.txt.

Analysis

Upon reviewing the outputs (reference_results.txt and iolatency_results.txt), it was observed that the results are very similar, indicating a high level of accuracy and reliability in our iolatency tool's measurements compared to the established reference.