Introduction In general, if we want to debug Linux Kernel, there are lots of tools such as Linux Perf, Kprobe, BCC, Ktap, etc, and we can also write kernel modules, proc subsystems or system calls for some specific debugging aims. However, if we have to instrument kernel to achieve our goals, usually we would not […]
Author: Weiwei Jia
71 posts in total.
QEMU/KVM Network Mechanisms
Introduction As we know, network subsystems are important in computer systems since they are I/O systems and need to be optimized with many algorithms and skills. This article will introduce how QEMU/KVM [2] network part works. In order to put everything simple and easy to understand, we will begin with several examples and then understand […]
I/O Microscopy: Tasks’ Disk I/O Information with High Accuracy
Abstract Most popular task monitor systems (such as top, iotop, proc, etc) can only get tasks’ disk I/O information like tasks’ I/O utilization percentage every seconds due to kernel timer/tick frequency and high time cost of system interfaces. This article presents I/O Microscopy, a new way to get tasks’ disk I/O information with high accuracy. […]
How does linux kernel collect task stats data
Motivation ∞ Recently, I find it is hard to know the percentage of time that one process uses to wait for synchronous I/O (eg, read, etc). One way is to use the taskstats API provided by Linux Kernel [1]. However, for this way, the precision may be one problem. With this problem, I dig into […]
x-data-plane feature in QEMU/KVM
Abstract In systems, sometimes, we use one global lock to keep synchronization among different threads. This principle also happens in QEMU/KVM (http://wiki.qemu.org/Main_Page) system. However, this may cause lock contention problem. The performance/scalability of whole system will be decreased. In order to solve this problem in QEMU/KVM, x-data-plane feature is designed/implemented, which the high-level idea is […]
The length of timeslices for processes under CFS process scheduling algorithm in Linux Kernel
Abstract As is known, CFS (Completely Fair Scheduling) is a famous process scheduling algorithm in Linux Kernel but there is no convenient way for developers to get the timeslices of processes if CFS is chosen. In this article, I will introduce one way to hack the timeslices of process easily for CFS in Linux Kernel. […]
How sched_min_granularity_ns, sched_latency_ns and sched_wakeup_granularity_ns in CFS affect the timeslice of processes
Abstract Currently, the most famous process scheduling algorithm in Linux Kernel is Completely Fair Scheduling (CFS) algorithm. The core idea of CFS is to let each process share the same proportional CPU resources to run so that it is fair to each process. In this article, I will introduce how sched_min_granularity_ns and sched_latency_ns work internal […]
How migration thread works inside of Linux Kernel
Abstract In computer systems, resources have to be balanced so that the performance will be better based on the same hardware. In Linux Kernel system, we will see some migration kernel threads running as daemons to do this kind of jobs as follows. In this article, we will discuss how Linux Kernel balances its hardware/software […]
How sched_setaffinity works inside of Linux Kernel
Abstract Sometimes, we may want to migrate one process/thread to one specific CPU for some specific purpose. In the Unix/Linux systems, you may choose sched_setaffinity to finish this job. This article will help you to understand how sched_setaffinity (or other APIs like pthread_setaffinity_np in user-space) works internal Linux kernel. Details — sched_setaffinity(pid_t pid, const struct […]
Infrastructure Software For Fedora
Fedora is a popular distro supported by the RedHat Corporation. This article recommends you some infrastructure software and how to install them in details. Minimize and Maximize window ∞ 1, Install software gnome-tweak-tool # yum install gnome-tweak-tool 2, Start gnome-tweak-tool and set minimizing and maximizing functions as follows. Actually, gnome-tweak-tool has more functions than what […]
Connecting to Remote Servers by VNC on Windows
Software you will need 1, Putty 2, Real VNC viewer 3, twm (lightweight desktop). On fedora (centos, redhat): sudo yum install twm (on other distros, you may need other commands, or download source code and install it). Specific steps ∞ 1, Enter your Host name and port in putty. 2, Set port forwarding in putty […]
