Shulou(Shulou.com)05/31 Report--

What is the comparison between Fedora and Ubuntu kernels? I believe many inexperienced people don't know what to do about it. Therefore, this article summarizes the causes and solutions of the problem. Through this article, I hope you can solve this problem.

Red Hat's Josh Boyer curiously compared the configuration differences between Fedora 18 and Kernel 3.8 on Ubuntu 13.04 and found something interesting.

Josh Boyer chooses 3.8.11-200.fc18 in current Fedora 18 and linux-image-3.8.0-19-generic in Ubuntu 13.04 to compare in X86 64-bit environment, both of which use the same upstream kernel.

Underlying settin

Ubuntu sets the number of kernels available for use to 256 and Fedora to 128, while Ubuntu enables more NUMA (inconsistent memory access) support and sets a higher number of NUMA supports. Given that Canonical intends to unify the kernels in Ubuntu desktop and server editions, it is perfectly understandable that Ubuntu enables these SMP-related options.

Fedora is set to 1000 for timer interrupt wake-up times and Ubuntu is set to 250th. Generally speaking, higher values mean faster interactive response and are more suitable for desktop applications, while smaller values make it easier for the server to focus on work rather than responding to interrupts. However, both enable on-demand response, and CPU will not be disturbed by useless timers when he is idle. In the future, it is estimated that both of them will gradually migrate to the zero timer wake-up introduced by the 3.10 kernel to better reduce the energy consumption during sleep.

At the same time, Ubuntu also enables the fast no HZ option by default, which increases the chance that the kernel will be idle and can reduce energy consumption. Fedora was enabled when this option was first introduced upstream, but it was disabled by a number of subsequent problems. After several kernel revisions, this feature is much more stable than it was and is worth reconsidering.

Default selection

The default Ubuntu scheduler is deadline and Fedora is CFQ (Completely Fair Queueing).

In terms of the default CPU frequency control strategy, Fedora follows the conventional on-demand regulation, while Ubuntu has a slightly different performance priority.

However, both of these items can be adjusted at run time, and what we are talking about here is only the default settings.

Linux security module

Not surprisingly, Fedora only enabled support for SELinux in the kernel.

Ubuntu is more "friendly" to enable support for all security modules, not just its default support of AppArmor. Although this will not lead to any security improvements, it gives system administrators more options in addition to the default security module.

Module signature

Both Fedora and Ubuntu use module signatures, but there are differences in specific applications.

Fedora uses SHA256 for module signing because this is the usual verification method used by UEFI.

Ubuntu uses the module version to determine whether the module is secure by comparing its CRC with the records in the kernel when loading the module. Ubuntu also enables the "source version" field, which, to some extent, allows modules to be compiled and loaded for different kernel versions, if the correspondence is clear.

Legacy system support

More support for unusually rare or abandoned devices, partitions, and networks is enabled than Fedora,Ubuntu, such as atari and sysv68 partitions, DECNET and ARCNET networks, and parallel IDE interfaces (editor's note: Linux used the SATA driver to implement IDE support about 8 years ago). However, Fedora also enables support for some legacy systems, such as OSS, and Ubuntu has completely disabled it.

In addition, the Ubuntu kernel also enables more SoC support by default, such as keyboards, GPIOLIB, MFD drivers, etc., which can only be seen in embedded areas, as well as JFFS2 and F2FS file systems. This seems to be at odds with Canonical's idea of merging the desktop version with the server version. But it also means that Ubuntu may be able to start up on some rare X86 SoC devices

In terms of open source graphics driver support, Fedora only enables those and a few FB drivers that support KMS, while Ubuntu enables almost all of them by default.

Ubuntu enables many kernel drivers in the Staging state by default. Staging saves open source drivers that are unable to enter mainline maintenance due to quality problems. Enabling it may lead to a wider range of hardware support, but it also introduces hidden dangers to system stability due to quality.

There is no significant difference in performance between the two cores in configuration, but some of the details deserve to be re-examined by both sides.

After reading the above, have you mastered the method of comparing Fedora and Ubuntu kernels? If you want to learn more skills or want to know more about it, you are welcome to follow the industry information channel, thank you for reading!

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