Change and selection of Linux-2.6.26

About the change of Linux-2.6.26 -- Linux general technology-Linux programming and kernel information, the following is a detailed reading. Author: xiaosuo

Linux 2.6.26 has been released for a while, but it has not summarized the changes it has brought. Today, I am idle, and I will try again later.

The emergence of mutex makes the synchronization primitive of the signal lamp (semaphore) less important to performance. In this case, the maintainability, debugging, and scalability of the Code become more important. In the end, the signal lights reproduced in C Language replaced the previous complex architecture-related implementation versions and entered the official kernel. Of course, the performance of the new C version cannot be the same as that of the old version, but this is not a problem, because Linus obviously encourages you to use a simpler mutex lock, avoid heavy and complex traffic signals. Although there are not many places to directly use traffic signals in the kernel, the impact of this change on Kernel performance cannot be ignored, mainly reflected in the big kernel Lock Based on Traffic Signals (BKL: big Kernel Lock), Linus considers that the legacy large Kernel Lock affects performance, rather than traffic signals, therefore, he advocates removing the large kernel lock that affects kernel scalability to eliminate the impact of this change. It's just a long history of the large kernel lock. It's easy to remove it. Otherwise, it will be removed from the kernel long ago. Fortunately, this has been paid attention by the main players, we believe that the large kernel lock may be removed within several development cycles, and we are waiting for this time. This also means that kernel Versions later than 2.6.26 need to be tested with caution before porting, to prevent the impact on system performance.

Syncookies for SYN Flood (Flood) Denial of Service (Deny) attacks (DoS) can support TCP options and IPv6, TCP options are supported by timestamps. In Linux, the default TCP congestion control algorithm CUBIC is updated to Version 2.2.

The biggest change in this kernel version is the built-in source code-level debugging tool KGDB. I wanted to write an article to explore its configuration and application. Later I found that jserv and hellwolf were both shot, so I was too lazy. In addition, hellwolf also mentioned that qemu can be used directly to debug the kernel. If the above documents are not authoritative enough, you can refer to the KGDB documentation.