Decrypt Linux kernel 2.4

Decrypt Linux kernel 2.4-general Linux technology-Linux programming and kernel information. For more information, see the following section. Author: Fang Han


With the continuous release of the Linux 2.4 kernel test version, the 2.4 kernel architecture, main features, and improvements have been roughly finalized. Supporting all 64-bit processors, enterprise-oriented, comprehensive integration of system resources, and the full version of Linux 2.4 kernel that requires less memory will open a beautiful new world for humans.

The latest stable Linux kernel version is 2.2.16, and the latest test version is 2.4-test3. This time, Linus learned a long lesson from the test version in the 2.1 series development. It jumped the 2.3 series directly from 2.3.49 to 2.3.99 and to 2.4-test4 in advance. This article will give a forward-looking introduction to the 2.4 series Kernel Based on 2.4-test4.

Compared with the improvement of the 2.2 series and the 2.0 series, the 2.4 series has made greater progress, but this also means that the 2.4 series will be difficult to be compatible with the 2.2 series. The improvements in the 2.4 series are mainly reflected in the system, network, and driver.

System

In terms of kernel architecture, 2.2.16 supports the following hardware platforms: Alpha, Arm, i386, M68k, Mips, Ppc, S390, iSCSI, and Sparc64. S390 is the MainFrame machine of IBM, and its addition is a recent task. 2.4 The major change was to support IA64. As Intel's next-generation server product, IA64 has attracted more and more attention from software vendors. Linux, as the first operating system to support IA64, proves the powerful vitality of Linux and is also a good opportunity for Linux to enter the enterprise-level market. Other new hardware platforms are Super-H and Mips64. In addition, they support Athlon/K7, Crusoe, and Winchip under i386. Crusoe is the mobile CPU launched by Transmeta, which is used by Linus. Linux continues to hold the leading position in supporting the most hardware platforms.

2.4 added support for full resource manager. Now, in the Linux kernel, the allocation of PCI and other resources will be more intelligent, which makes plug-and-play a better support for Linux. In addition, Linux has changed the original disk buffer mechanism, from a complicated dual-buffer system to a simple and practical single-buffer system. The scalability of Linux on multi-processor is enhanced to provide a configurable process management mechanism. The process scheduling mechanism has been completely rewritten, which improves the scheduling efficiency of the kernel and greatly increases the number of concurrent processes supported. The number of users supported by the Linux kernel reaches the power of 32, and the maximum number of files supported is also removed from the limit of 2 GB. The supported CPU is 32 and the memory is 64 GB. It also supports 16 Ethernet cards, 22 IDE devices, and a multi-IO-APIC (Advanced Programmable Interrupt Controller ). Its support for Share Memory has also changed to loading a special file system to/var/shmem, which makes it more compatible. Another far-reaching change was the addition of DEVFS. The so-called DEVFS is to change the current/dev directory into a file system. You no longer need to manually add device files to a new device, and the kernel will automatically add files to the file system. The directory structure has also changed. For example,/dev/hda will be moved to/dev/ide0/disk0 /...... This makes it easier to add USB, IEEE1394, and other devices to Linux. But at the same time, a large number of applications need to be modified to use this new feature.

A major improvement in the file system is the support of LVM (Logic Volume Manager. The file system running on LVM spans the disk and can dynamically scale the file system size and increase the file system size at runtime. This has become an enterprise standard for HP-UX and Compaq True64 UNIX. In fact, many features of LVM are supported in Linux's MD (Multi Disk), but this will be an important basis for commercial users to adopt Linux. The support for RAID (redundant disk array) has also been enhanced, which optimizes the execution efficiency of the RAID sub-system and achieves RAID 0, 1, and 4/5. Multi-threaded Multi-processor is enhanced, and RAID devices can be directly used as the root partition for startup. In addition, raw io support has been added, which is a feature that many commercial software urgently need, such as Oracle databases. The partition system supported by Linux supports UDF (file system used by DVD), which enables Linux to support the DVD system. It is disappointing that the two existing Log File Systems (ext3/reiserfs) are still not merged into Kernel 2.4, which causes many developers to complain about the connection.

Network

In terms of network, Linux has made a lot of improvements to the evaluation results of the same WinNT in the previous period. The most important technology is the "wake one" technology, which greatly improves the efficiency of the WWW server. KHTTPD is supported so that Linux can provide access to static Web pages at the kernel level. This is a good alternative for servers with huge traffic volumes, such as servers dedicated to providing image services.

In Linux, the IP firewall and IP disguise technology have been modified again (this is the third time that the Linux kernel has re-designed this part). The current name is IP Table. It is still compatible with ipfwadm of 2.0 and ipchains of 2.2, and many vrouters can now be implemented. For enterprise users, DECNET, ARCNET, NetBui, SMB, and so on are all supported. Especially the rewrite of SMB will greatly enhance the network performance of Windows9x/NT/2000.

Hardware

Currently, 2.4 supports the following USB devices: mouse, keyboard, digital device, scanner, printer, Bluetooth device, MP3 player, tablet, Nic, USB interconnect cable, game lever, USB parallel/serial port, digital camera, camera, sound card, Modem, hard drive, usb hub, soft drive, optical drive, etc. 2.4 support for I2O and Fimwire (IEEE1394) has also been implemented. After a developer contributes 50 thousand lines of code, ACPI has been greatly improved in version 2.4-test4. Other support, such as NIC, scsicard, RAID card, and ide raid, has also improved significantly. Currently, the kernel supports UDMA66, ATA100, and ide raid. Many developers have to port the 2.4 series drivers to the 2.2 series. Kernel eventually combines PCMCIA support into the official version, which is of great significance to notebook users. It is worth noting that the sound card has not been greatly improved in 2.4, and I believe that only the merger of the ALSA Plan (www.alsa-project.org) can be greatly improved.

In addition, the following plans are not included in version 2.4:

Kernel Lever Encrypt Support (www.kerneli.org)

Reiser Log File System (www.devlinux.com)

Ext3 Log File System

Linux Virtual Server (www.linuxvirtualserver.org)

Linux security monitoring system (www.lids.org)

Linux Virtual Server and Linux security monitoring systems are GNU programs led by young Chinese hackers. They are Zhang Wenyu and Xie huagang. We hope they will soon become the first Linux developers in China to mark their names in the kernel.

The release date of Linux 2.4 is not yet determined, and we believe it is at the end of the third quarter of this year. At that time, it would be time for Linux to fully enter the enterprise-level market and the desktop market. However, users may not immediately enjoy the 2.4 series kernel. This also depends on the speed of the major Linux release vendors. After all, every migration is a painful process for Linux release vendors. But at the end of this year, we should be able to see the Linux release version using the 2.4 series kernel. Let's wait and see it!