Optimizing the Linux Kernel
Ready-to-Use Patch Sets
Manual kernel configuration is a good way to learn about the kernel. However, if you want to play it a little safer and don't have time for a deep dive, several performance-optimized custom kernels are available for download. Two popular patch sets are XanMod and Liquorix.
The overall benefit of using a custom Linux kernel will vary depending on the workload. The average boost in synthetic tests may be around five percent, but the difference in experience (for example, the start time for Firefox while playing a high-resolution video in the background) might be considerably more significant. Keep in mind that many of the described optimization techniques that involve different scheduling and changing inner kernel timers only show up when the system has a significant load. The best way to conduct a simple home-grown benchmark is to set up a resource-hogging process, such as video encoding or a huge file compression, and then try to do some normal browsing along with it. Custom-patched kernels will likely deliver a smoother experience and maintain responsiveness even if CPU usage is nearly 100 percent.
As for real-world benchmarks, I conducted a series of tests using the sysbench tool. Sysbench can stress test Linux systems and test CPU, memory, threads, and I/O performance. The tests were run against three flavors of the 5.12 kernel: the mainline Ubuntu kernel, the XanMod kernel, and the Liquorix kernel. Table 1 shows the sysbench results for my test system running on Intel Xeon E5450 with 4GB of memory and with Pop!_OS 20.04 installed on a budget SSD drive. Keep in mind that these results are from my tests run on my hardware. The developers of these projects will likely have their own tests for specific scenarios in which their kernels excel.
Table 1
Comparing Kernels
5.12.14-051214-generic | 5.12.14-xanmod1 | 5.12.0-14.2-liquorix |
|
---|---|---|---|
CPU operations per second |
352683.54 |
357276.58 |
357004.96 |
Threads: number of events |
17351 |
17364 |
24252 |
Memory: min latency (less is better) |
0.65 |
0.61 |
0.38 |
Memory: max latency (less is better) |
433.60 |
251.99 |
286.81 |
File I/O: writes per second |
6266.96 |
6386.38 |
5794.37 |
It is clear that all three kernels run very close to each other when measured for CPU performance, with XanMod only 1.3 percent faster than the generic kernel. In the threads test, the contenders showed different results as long as each used its own process/thread scheduler. The vanilla Linux kernel comes with the completely fair scheduler (CFS), which turned out to be on par with XanMod's CacULE (enhanced ULE scheduler originally derived from FreeBSD), but both lost the race to the Multiple Queue Skiplist Scheduler (MuQSS) enabled in Liquorix. It turns out that in a densely threaded environment, MuQSS scores up to 40 percent better than its rivals.
When it comes to memory latencies, you can clearly see that both kernel flavors performance-wise try their best to reduce the maximum latency value. In that regard, the record belongs to XanMod, but the average latency is still lower in Liquorix. The I/O test for sequential writing then showed that XanMod was actually more balanced, and it delivered the best throughput figures, whereas Liquorix yielded 10 percent less write speed. By the way, both XanMod and Liquorix were using Budget Fair Queues (BFQs) for handling disk loads, whereas the generic kernel stuck with mq-deadline
. So, in the end, the choice comes down to the acceptable throughput trade-off for the sake of better responsiveness. Regardless of your choice, both the customized kernels will run faster than the generic kernel.
Conclusion
Linux was created for hacking and tinkering, and users still have many options for tweaking the Linux kernel. This article touched on a few important options, and you will find many more if you spend some time with the Linux kernel configuration menu and browse the kernel documentation [6]. Just remember that it is better to test these techniques first on a non-critical system before you roll them out on your production network.
Infos
- I/O Schedulers: https://wiki.ubuntu.com/Kernel/Reference/IOSchedulers
- Spectre: https://en.wikipedia.org/wiki/Spectre_(security_vulnerability)
- Meltdown: https://en.wikipedia.org/wiki/Meltdown_(security_vulnerability)
- XanMod: https://xanmod.org/
- Liquorix: https://liquorix.net/
- Linux Kernel documentation: https://www.kernel.org/doc/
« Previous 1 2 3 4
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.
News
-
So Long Neofetch and Thanks for the Info
Today is a day that every Linux user who enjoys bragging about their system(s) will mourn, as Neofetch has come to an end.
-
Ubuntu 24.04 Comes with a “Flaw"
If you're thinking you might want to upgrade from your current Ubuntu release to the latest, there's something you might want to consider before doing so.
-
Canonical Releases Ubuntu 24.04
After a brief pause because of the XZ vulnerability, Ubuntu 24.04 is now available for install.
-
Linux Servers Targeted by Akira Ransomware
A group of bad actors who have already extorted $42 million have their sights set on the Linux platform.
-
TUXEDO Computers Unveils Linux Laptop Featuring AMD Ryzen CPU
This latest release is the first laptop to include the new CPU from Ryzen and Linux preinstalled.
-
XZ Gets the All-Clear
The back door xz vulnerability has been officially reverted for Fedora 40 and versions 38 and 39 were never affected.
-
Canonical Collaborates with Qualcomm on New Venture
This new joint effort is geared toward bringing Ubuntu and Ubuntu Core to Qualcomm-powered devices.
-
Kodi 21.0 Open-Source Entertainment Hub Released
After a year of development, the award-winning Kodi cross-platform, media center software is now available with many new additions and improvements.
-
Linux Usage Increases in Two Key Areas
If market share is your thing, you'll be happy to know that Linux is on the rise in two areas that, if they keep climbing, could have serious meaning for Linux's future.
-
Vulnerability Discovered in xz Libraries
An urgent alert for Fedora 40 has been posted and users should pay attention.