Read more at: https://www.ebpf.top/post/cpu_io_wait 1. Definition of I/O Wait 2. Test and Verification 3. Further Clarification on Disk Throughput and Processes with High I/O FrequencyAfter identifying process I/O wait conditions through the vmstat b column, we can further define them using iostat and iotop. 4. Analysis of Kernel CPU Statistics Implementation 5. Conclusion References 1. Definition of I/O Wait I/O Wait is a performance metric for a single CPU, indicating the idle time consumed when threads in the CPU dispatch queue (in the sleep state) are blocked on disk I/O. The CPU’s idle time is divided into truly idle time and time spent blocked on disk I/O. A higher CPU I/O Wait time indicates a possible bottleneck in the disk, causing the CPU to wait idle. If you find this definition a bit confusing, then please continue reading. I believe that after you read the testing and verification process in this article, your understanding of the above definition will be different.……

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This article can be found at: https://www.ebpf.top/post/ftrace_kernel_dynamic 1. Basic Knowledge 1.1 Default Compilation 1.2 Using the -pg Option 1.3 Using the -pg and -mfentry Options 1.4 Kernel Verification 2. Validation of kprobe tracing mechanism in ftrace 3. Validation using a Kernel Module 3.1 Using kallsyms_lookup_name 3.2 Using Kernel Function Addresses Directly (Pitfalls, Optional) 4. Verification using gdb + qemu Reference In the Geek Time’s “Mastering Container Battles” by Teacher Li Chengyuan, a pondering question was left in the extra session 04 | Understanding ftrace(2): How to Understand the Technology Behind ftrace Tracepoint and kprobe?: Consider this, how can we observe that the first instruction of the corresponding kernel function has been replaced after we register a probe with kprobe for it? Kprobe is a mechanism for dynamic tracking of kernel functions. By using this mechanism, almost all kernel functions can be tracked (excluding those annotated with __kprobes/nokprobe_inline and those marked with NOKPROBE_SYMBOL).……

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