Linux 2.4 kernel-kernel improvements

The Linux 2.4 kernel provides a better description than the kernel-Linux general technology-Linux programming and kernel information. For more information, see the following. 1. Module Subsystem, Unified Device Model, and PnP support Module Subsystem have undergone major changes.

2. Improved Stability
To completely prevent the kernel from loading or exporting the kernel module in use, or at least to reduce the possibility of using the module while loading or detaching the module (which sometimes causes system crash ), the process of loading and exporting kernel modules has been improved.

I always thought that Linux would not crash until my 2.4-core Linux suddenly crashed, causing significant losses. Therefore, it is strongly recommended that all Linux Application Systems Based on the 2.4 kernel upgrade the kernel immediately. Be sure to back up the system before the upgrade to prevent major losses caused by upgrade errors, to prevent hardware incompatibility and application system incompatibility problems, you 'd better test the problem before going online!

3. Unified Device Model
Creating a unified device model is one of the most important changes to the 2.6 kernel. It promotes the standardization of module interfaces and aims to better control and manage devices, for example, more accurate identification of system devices. Power Management and device power status. Improved system bus structure management.

4. Support for plug-and-play (PnP)
Linux running the 2.6 kernel becomes a real plug-and-play OS. For example, PnP support for ISA PnP extensions, legacy MCA and EISA buses, and hot swapping devices.

5. kernel infrastructure changes
To distinguish regular object files with the. o extension, the kernel module now uses the. ko extension. A new sysfs file system is created, which is described when the kernel discovers the Device Tree. Memory, NUMA, and more RAM. 2.6 The kernel supports a larger number of RAM resources, up to 64 GB in paging mode.

6. NUMA
Support for Non-Uniform Memory Access-NUMA systems with inconsistent kernel Access is a new feature in kernel 2.6.

7. Thread model, NPTL
Compared with LinuxThreads of v2.4, NPTL (Native POSIX Threading Library) is newly introduced in version 2.6 ). NPTL provides enterprise-level thread support for Linux and provides far better performance than LinuxThreads. It is based on a ratio of between users and kernel threads.

In October 2003, NPTL support was incorporated into the gnu c library glibc, and Red Hat was the first to implement NPTL using a customized v2.4 kernel in Red Hat Linux 9 and Red Hat Enterprise Linux.

8. Performance Improvement
The new scheduler algorithm, 2.6 Linux kernel introduces the new O (1) algorithm. It runs very well under high loads. The new scheduler distributes time slices based on each CPU. This eliminates global synchronization and reallocation cycles, thus improving performance.

Kernel Preemption. The new 2.6 Kernel is preemptible. This will significantly improve the performance of interactive and multimedia applications.

I/O performance is improved, and the Linux I/O subsystem has also undergone major changes, by modifying the I/O scheduler, you can ensure that no process will reside in the queue for too long to wait for input/output operations, so that the I/O operation can respond more quickly.

Fast User-Space Mutexes (Fast User-Space Mutexes) and "futexes" (Fast User-Space mutex) can serialize threads to avoid race conditions. Introducing it also improves the response speed. "Futexes" is partially implemented in the kernel space to allow improvements based on competition to set the priority of waiting tasks.

9. scalability Improvement
With more processors, Linux kernel 2.6 supports up to 64 CPUs. Support for larger memory, thanks to PAE (Physical Address extension, Physical Address Extensions), The supported memory is increased to 64 GB in paging mode on a 32-bit system.
The number of users and groups increases from 65,000 to more than 4 billion, that is, from 16-bit to 32-bit.

The number of PID, the maximum number of PID increased from 32,000 to 1 billion.

The number of opened file descriptors. The number of opened file descriptors does not increase, but you do not need to set this parameter in advance. It will be adjusted by itself.

10. Support for more devices
Before Linux kernel 2.6, there are restrictions on large systems in the kernel, such as 256 devices per chain. The v2.6 kernel completely breaks these restrictions, not only supports more types of devices, but also supports more devices of the same type. In Linux 2.6, 4095 supports 1 million main device types, each of which can have more than sub-devices. The file system size. The maximum size of the addressable file system allowed by Linux kernel 2.6 is 16 TB.

11. File System
Traditional Linux file systems such as ext2, ext3, and ReiserFS have been significantly improved. The most noteworthy improvement is the introduction of extended attributes (or file metadata. The most important thing is the implementation of posix acl, which is an extension of common UNIX permissions and supports more refined user access control.

12. In addition to the improved support for traditional Linux file systems, the new kernel fully supports relatively new XFS file systems in Linux. The Linux 2.6 kernel also introduces improved support for the NTFS file system. Now, the NTFS file system can be installed in read/write mode.