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Summary This article systematically documents how I turned a Raspberry Pi 5 into a minimal development and testing platform for the mainline Linux kernel (Vanilla Kernel) — including repository trimming strategies, custom kernel configuration, cross-compilation and automated deployment scripts, overlay removal techniques, and long-term synchronization with the mainline community. It’s aimed at geeks interested in the Linux mainline, ARM64 adaptation, kernel development, upstream contribution, or anyone who loves tinkering with the kernel. ...

In certain scenarios, we may need to set up a chained VPN structure: first connecting internal devices to a self-hosted WireGuard server (e.g., a personal VPS), then routing all traffic through that server to another VPN (a corporate, school, or commercial VPN service) before reaching the internet. Building this “VPN over VPN” network architecture offers the following clear advantages: Robust Privacy Protection: Internal devices’ data flows are first encrypted through a self-hosted WireGuard tunnel to your personal VPS. Then, the VPS forwards it again through a corporate or commercial VPN before finally exiting to the internet via that VPN’s IP address. This method completely avoids using the VPS’s own IP address to access target networks, greatly reducing the risk of your personal IP being tracked or leaked. ...

Generally speaking, we always tend to follow the path taken by others. Once we deviate from what everyone considers to be the right path, we feel that we are in a state of suspension and consider ourselves to be in a state of danger. We tend to think that a certain mainstream idea that everyone has is correct, without thinking about why it is correct and the logic behind those ideas. While conforming to the mainstream way can lead to some results, this way is not always best for you and you may just be following blindly. If someone asks for your advice, you may state these mainstream ways without thinking, but when someone asks you why they are correct, you may not know how to answer. ...

Recently, compliance requirements have been creeping into the technical side of things. In recent times, there are always products coming to the table about implementing such and such compliance requirements. Or, do some kind of compliance questionnaire. I feel that compliance is mainly about the storage of user information, access needs to be standardized, and then users can gradually start to control their own data. And then there are some personnel, organizational changes on the technical level of the impact of changes, for example, a business has been dispatched to other departments, and then we have been and this business to share the database and other resources. At this time, the issue of cost comes to the fore, that is, the money should be counted over there. Although it is a company, a business group, but I feel that perhaps due to the company’s internal accounting mechanism, for these cost issues are still more serious, will always argue what: they use our database, the money is still on our side and so on. ...

This week I realized that some of the service frameworks are not written very well, especially certain Java frameworks. When the CPU usage reaches about 40%, there are a lot of timeouts. These services, CPU cores and memory capacity is not not enough, the number of working threads is not not enough. However, it is not enough to run the CPU. Using Java performance tools to analyze the discovery, in fact, found that most of the working threads in Idle or Waiting state. At present, the comprehensive analysis of all the circumstances, still puzzled. NIO is also used, also used the Netty framework, but the throughput is not up. Through the analysis of threads, found that there is no particularly busy business threads. Inference should be IO or some kind of waiting mechanism to cause this low processing efficiency. ...

This week was focused on dealing with a risk item that was discovered before the holidays. A service that was using Redis and not setting a TTL for the key, but was banking on the Redis elimination policy. I see that this service is using Redis with an LRU elimination strategy set up. This strategy may seem perfect, but there are pitfalls when there is a lot of write traffic for a certain shorter period of time. ...

From the end of January to the beginning of February, it falls under the Chinese New Year. During this period, the person responsible for securing the operation of the Spring Festival phase needs to be on call to deal with online issues. I was in a constant state of worry, and the good thing is that online problems did not come to me actively. Maintaining overall immobility throughout the Chinese New Year is the best. ...

Kubernetes (k8s) is a popular container orchestration platform that allows developers to deploy, manage, and automate containerized applications in a cloud environment. In Kubernetes, CPU resource allocation is a critical issue that directly affects the performance and reliability of applications. In this article, we will introduce the CPU resource allocation mechanism in Kubernetes, including CPU requests and limits, the CPU Share mechanism, and CPU schedulers and other related concepts, to help developers better control the CPU allocation of containers, so as to improve the performance and reliability of applications. ...

This week was mainly about ensuring the stability of various services in the run up to the Chinese New Year. Recently, I found that a certain service often reported timeout during peak traffic hours, and I reminded to forward to the service owner to deal with it. But after a few days, the service owner still couldn’t explain the reason. I had to deal with this problem personally, because the alarm has been very serious, and the timeout rate of some nodes can reach 20%. In this period of time, it should be due to the approaching holidays, the traffic has risen significantly, compared with the end of December has risen by 100%. So first of all, it is suspected that the carrying capacity of the service is insufficient, so it first carried out a capacity expansion. ...

As we move into 2023, this year is going to be a tough one. This year will face several challenges, one is to migrate all the data previously deployed on physical servers to the cloud. Then there’s the accelerated development of several new team members who will be able to take on the services involved in the current main business as soon as possible and will be expected to be able to independently resolve user issues and optimize the services. This will allow me to transfer some of the work to them and focus on important goals that are expected to take a long time this year. ...