Welcome!

Linux Containers Authors: Pat Romanski, Liz McMillan, Gerardo A Dada, SmartBear Blog, Elizabeth White

Related Topics: Linux Containers

Linux Containers: Article

The kernel of pain

Let's call a spade a spade: For large servers, the 2.4 kernel has been a disaster.

(LinuxWorld) -- Let's start from the beginning. In July 2001, I was responsible for upgrading a customer's server from Red Hat 6.2 to Mandrake 8.0. The machine was built from scratch, and Mandrake was installed onto a freshly formatted RAID 5 array. We then migrated the Red Hat 6.2 applications to the new machine.

After a little configuration, the machine seemed to run fine. We successfully migrated the entire system in less than five hours. Considering this was a large-scale server, that was quite a feat and was certainly welcomed by our paying customer.

However, after about a month into deployment I started noticing strange problems with the machine. Intermittent lockups were the most common. The lockups appeared physical, and the machine was unrecoverable without a reboot.

While performing research on the problem, I learned there was a serious sync() bug in the 2.4 kernel. This bug exists in all kernel 2.4 versions until 2.4.6. The solution seemed simple: I upgrade the kernel.

About a week later, the machine locks up cold -- again. We considered it a fluke and rebooted. The very next day the machine locked up -- again. We do further research and find that the original 2.4 VM (Virtual Memory) implementation was causing problems. In my frustration and embarrassment, I would be inclined to call it bad design, but I don't know enough about the intricacies of the Linux kernel to say whether it was.

The VM problem was so horribly bad that the kernel team decided to rip out the older implementation and implement a completely new design. These problems continued as the kernel versions worked their way up through 2.4.11, which has a serious symlink bug that could lead to corrupted inodes. As of 2.4.13, things finally seemed to be cleaned up a bit. The kernel seemed to show more stability. Then we hit kernel 2.4.15.

Linux version 2.4.15 contained a bug that was arguably worse than the VM bug. Essentially, if you unmounted a file system via reboot -- or any another common method -- you would get filesystem corruption. A fix, called kernel 2.4.16, was released 24 hours later.

Kernel 2.4.16 now appeared to be the kernel of choice. It seemed as if it was possible that after almost a year of "stable" status that the 2.4 kernel would be usable in a production environment.

We still aren't there yet

Alas, the mire of trouble within the 2.4 series kernels continues. As of kernel 2.4.16, there is a serious bug in the OOM that can cause system lockups. The lock-up bug in 2.4.16 has supposedly been fixed in 2.4.17pre4aa1.

The current kernel release is 2.4.17, and one would hope that it is stable, but a brief review of the changelog will show that the kernel team is still working on fine-tuning the new VM design, and the vast amount of changes that have been made are already making me weary of it.

As I reviewed the archives of late December, I found that the per-user limit support in the 2.4 series kernels is broken. With the limit support broken, any user -- privileged or not -- has the potential to suck up all of the machines resources, effectively causing an intramural DoS (Denial of Service) attack. They could do this accidentally, and it would cause a great deal of grief for any system administrator.

So, what does all of this mean for me? It means that after five months of battling the new, better-than-fresh-butter, enterprise-ready 2.4 kernel, I am moving my customer back to the stodgy, conservative, more-enterprise-ready-than-2.4-has-been-since-its-release-almost-a-year-ago, 2.2 kernel-based Red Hat 6.2.

The 2.2 kernels may not handle large SMP machines as well, they may not handle large amounts of memory well (only 2 gigabytes), and they may have a practical limit of 2 gigabytes on a single file, but the 2.2. kernels don't crash or cause phone calls at 5:00 AM. Moreover, the 2.2 kernels don't make customers unhappy that they chose Linux as their server solution.

What does this mean for you?

What does all of this mean for you? That is your decision. You just read mine.

I hope Red Hat, SuSE, and Mandrake are taking a long hard look at the 2.4 process and formulating long-term plans to circumvent problems like this. I know, for example, that Red Hat has its own stress testing for the kernel, and that the Red Hat-shipped kernel is a fork of the standard Linux kernel. This fork is a good thing, because it means that Red Hat is able to apply patches that, in theory, make its kernel more stable.

On the desktop that I write this article, I am running Red Hat 7.2 with the 2.4.9-enterprise kernel. (It's a long story that involves this machine's AMD Duron processor.) I have yet to have any lockups on the Red Hat kernel since I upgraded to 2.4.9. I can say that Red Hat 7.2 seems reasonable and usable (at least as a desktop machine) but I am unsure if any 2.4 kernel-based system would be considered acceptable in a production server environment today.

More Stories By Joshua Drake

Joshua Drake is the co-founder of Command Prompt, Inc., a PostgreSQL and Linux custom development company. He is also the current author of the Linux Networking HOWTO, Linux PPP HOWTO, and Linux Consultants HOWTO. His most demanding project at this time is a new PostgreSQL book for O'Reilly, 'Practical PostgreSQL'

Comments (0)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


@ThingsExpo Stories
A critical component of any IoT project is what to do with all the data being generated. This data needs to be captured, processed, structured, and stored in a way to facilitate different kinds of queries. Traditional data warehouse and analytical systems are mature technologies that can be used to handle certain kinds of queries, but they are not always well suited to many problems, particularly when there is a need for real-time insights.
Big Data, cloud, analytics, contextual information, wearable tech, sensors, mobility, and WebRTC: together, these advances have created a perfect storm of technologies that are disrupting and transforming classic communications models and ecosystems. In his session at @ThingsExpo, Erik Perotti, Senior Manager of New Ventures on Plantronics’ Innovation team, provided an overview of this technological shift, including associated business and consumer communications impacts, and opportunities it ...
You think you know what’s in your data. But do you? Most organizations are now aware of the business intelligence represented by their data. Data science stands to take this to a level you never thought of – literally. The techniques of data science, when used with the capabilities of Big Data technologies, can make connections you had not yet imagined, helping you discover new insights and ask new questions of your data. In his session at @ThingsExpo, Sarbjit Sarkaria, data science team lead ...
Extracting business value from Internet of Things (IoT) data doesn’t happen overnight. There are several requirements that must be satisfied, including IoT device enablement, data analysis, real-time detection of complex events and automated orchestration of actions. Unfortunately, too many companies fall short in achieving their business goals by implementing incomplete solutions or not focusing on tangible use cases. In his general session at @ThingsExpo, Dave McCarthy, Director of Products...
Is your aging software platform suffering from technical debt while the market changes and demands new solutions at a faster clip? It’s a bold move, but you might consider walking away from your core platform and starting fresh. ReadyTalk did exactly that. In his General Session at 19th Cloud Expo, Michael Chambliss, Head of Engineering at ReadyTalk, will discuss why and how ReadyTalk diverted from healthy revenue and over a decade of audio conferencing product development to start an innovati...
WebRTC is bringing significant change to the communications landscape that will bridge the worlds of web and telephony, making the Internet the new standard for communications. Cloud9 took the road less traveled and used WebRTC to create a downloadable enterprise-grade communications platform that is changing the communication dynamic in the financial sector. In his session at @ThingsExpo, Leo Papadopoulos, CTO of Cloud9, discussed the importance of WebRTC and how it enables companies to focus...
SYS-CON Events announced today that 910Telecom will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Housed in the classic Denver Gas & Electric Building, 910 15th St., 910Telecom is a carrier-neutral telecom hotel located in the heart of Denver. Adjacent to CenturyLink, AT&T, and Denver Main, 910Telecom offers connectivity to all major carriers, Internet service providers, Internet backbones and ...
SYS-CON Events announced today that LeaseWeb USA, a cloud Infrastructure-as-a-Service (IaaS) provider, will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. LeaseWeb is one of the world's largest hosting brands. The company helps customers define, develop and deploy IT infrastructure tailored to their exact business needs, by combining various kinds cloud solutions.
Manufacturers are embracing the Industrial Internet the same way consumers are leveraging Fitbits – to improve overall health and wellness. Both can provide consistent measurement, visibility, and suggest performance improvements customized to help reach goals. Fitbit users can view real-time data and make adjustments to increase their activity. In his session at @ThingsExpo, Mark Bernardo Professional Services Leader, Americas, at GE Digital, discussed how leveraging the Industrial Internet a...
The cloud market growth today is largely in public clouds. While there is a lot of spend in IT departments in virtualization, these aren’t yet translating into a true “cloud” experience within the enterprise. What is stopping the growth of the “private cloud” market? In his general session at 18th Cloud Expo, Nara Rajagopalan, CEO of Accelerite, explored the challenges in deploying, managing, and getting adoption for a private cloud within an enterprise. What are the key differences between wh...
SYS-CON Events announced today that Venafi, the Immune System for the Internet™ and the leading provider of Next Generation Trust Protection, will exhibit at @DevOpsSummit at 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Venafi is the Immune System for the Internet™ that protects the foundation of all cybersecurity – cryptographic keys and digital certificates – so they can’t be misused by bad guys in attacks...
The best-practices for building IoT applications with Go Code that attendees can use to build their own IoT applications. In his session at @ThingsExpo, Indraneel Mitra, Senior Solutions Architect & Technology Evangelist at Cognizant, provided valuable information and resources for both novice and experienced developers on how to get started with IoT and Golang in a day. He also provided information on how to use Intel Arduino Kit, Go Robotics API and AWS IoT stack to build an application tha...
Amazon has gradually rolled out parts of its IoT offerings in the last year, but these are just the tip of the iceberg. In addition to optimizing their back-end AWS offerings, Amazon is laying the ground work to be a major force in IoT – especially in the connected home and office. Amazon is extending its reach by building on its dominant Cloud IoT platform, its Dash Button strategy, recently announced Replenishment Services, the Echo/Alexa voice recognition control platform, the 6-7 strategic...
IoT generates lots of temporal data. But how do you unlock its value? You need to discover patterns that are repeatable in vast quantities of data, understand their meaning, and implement scalable monitoring across multiple data streams in order to monetize the discoveries and insights. Motif discovery and deep learning platforms are emerging to visualize sensor data, to search for patterns and to build application that can monitor real time streams efficiently. In his session at @ThingsExpo, ...
For basic one-to-one voice or video calling solutions, WebRTC has proven to be a very powerful technology. Although WebRTC’s core functionality is to provide secure, real-time p2p media streaming, leveraging native platform features and server-side components brings up new communication capabilities for web and native mobile applications, allowing for advanced multi-user use cases such as video broadcasting, conferencing, and media recording.
Verizon Communications Inc. (NYSE, Nasdaq: VZ) and Yahoo! Inc. (Nasdaq: YHOO) have entered into a definitive agreement under which Verizon will acquire Yahoo's operating business for approximately $4.83 billion in cash, subject to customary closing adjustments. Yahoo informs, connects and entertains a global audience of more than 1 billion monthly active users** -- including 600 million monthly active mobile users*** through its search, communications and digital content products. Yahoo also co...
There will be new vendors providing applications, middleware, and connected devices to support the thriving IoT ecosystem. This essentially means that electronic device manufacturers will also be in the software business. Many will be new to building embedded software or robust software. This creates an increased importance on software quality, particularly within the Industrial Internet of Things where business-critical applications are becoming dependent on products controlled by software. Qua...
In addition to all the benefits, IoT is also bringing new kind of customer experience challenges - cars that unlock themselves, thermostats turning houses into saunas and baby video monitors broadcasting over the internet. This list can only increase because while IoT services should be intuitive and simple to use, the delivery ecosystem is a myriad of potential problems as IoT explodes complexity. So finding a performance issue is like finding the proverbial needle in the haystack.
Machine Learning helps make complex systems more efficient. By applying advanced Machine Learning techniques such as Cognitive Fingerprinting, wind project operators can utilize these tools to learn from collected data, detect regular patterns, and optimize their own operations. In his session at 18th Cloud Expo, Stuart Gillen, Director of Business Development at SparkCognition, discussed how research has demonstrated the value of Machine Learning in delivering next generation analytics to imp...
Large scale deployments present unique planning challenges, system commissioning hurdles between IT and OT and demand careful system hand-off orchestration. In his session at @ThingsExpo, Jeff Smith, Senior Director and a founding member of Incenergy, will discuss some of the key tactics to ensure delivery success based on his experience of the last two years deploying Industrial IoT systems across four continents.