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In Linux Kernel vs. Memory Fragmentation (Part I), I concluded that grouping by migration types only delays memory fragmentation, but does not fundamentally solve it. As the memory fragmentation increases and it does not have enough contiguous physical memory, performance degrades.
Therefore, to mitigate the performance degradation, the Linux kernel community introduced memory compaction to the kernel.
If you need to dynamically trace Linux process system calls, you might first consider strace. strace is simple to use and works well for issues such as "Why can't the software run on this machine?" However, if you're running a trace in a production environment, strace is NOT a good choice. It introduces a substantial amount of overhead. According to a performance test conducted by Arnaldo Carvalho de Melo, a senior software engineer at Red Hat, the process traced using strace ran 173 times slower, which is disastrous for a production environment.
So are there any tools that excel at tracing system calls in a production environment? The answer is YES. This blog post introduces perf and traceloop, two commonly used command-line tools, to help you trace system calls in a production environment.
Linux's memory management system is clear to the user. However, if you're not familiar with its working principles, you might meet unexpected performance issues. That's especially true for sophisticated software like databases. When databases are running in Linux, even small system variations might impact performance.
After an in-depth investigation, we found that Transparent Huge Page (THP), a Linux memory management feature, often slows down database performance. In this post, I'll describe how THP causes performance to fluctuate, the typical symptoms, and our recommended solutions.
Distributed clusters might encounter performance problems or unpredictable failures, especially when they are running in the cloud. Of all the kinds of failures, kernel failures may be the most difficult to analyze and simulate.
A practical solution is Berkeley Packet Filter (BPF), a highly flexible, efficient virtual machine that runs in the Linux kernel. It allows bytecode to be safely executed in various hooks, which exist in a variety of Linux kernel subsystems. BPF is mainly used for networking, tracing, and security.
