Last couple of years, we have witnessed an onslaught of vulnerabilities in the design and architecture of cpus. It is interesting and surprising to note that the vulnerabilities are mainly targeting the features designed to improve the performance of cpus - most notable being the hyperthreading(smt). While some of the vulnerabilities could be mitigated in software and cpu microcodes, couple of...
Understanding Application performance and utilization characteristics is critically important for cloud-based computing infrastructure. Minor improvements in predictability and performance of tasks can result in large savings. Google runs all workloads inside containers and as such, cgroup performance monitoring is heavily utilized for profiling. We rely on two approaches built on Linux...
The printk() function has a long history of issues and has undergone many iterations to improve performance and reliability. Yet it is still not an acceptable solution to reliably allow the kernel to send detailed information to the user. And these problems are even magnified when using a real-time system. So why is printk() so complicated and why are we having such a hard time finding a good...
For the past couple of years the CKI ("cookie") project at Red Hat has been transforming the way the company tests kernels, going from staged testing to continuous integration. We've been testing patches posted to internal maillists, responding with our results, and last year we started testing stable queues maintained by Greg KH, posting results to the "stable" maillist.
Now we'd like to...
The RDMA subsystem in Linux (drivers/infiniband) is now becoming widely used and deployed outside its traditional use case of HPC. This wider deployment is creating demand for new interactions with the rest of the kernel and many of these topics are challenging.
This talk will include a brief overview of RDMA technology followed by an examination & discussion of the main areas where the...
The BPF VM in the kernel is being used in ever more scenarios where running a restricted, validated program in kernel space provides a super powerful mix of flexibility and performance which is transforming how a kernel work.
That creates challenges for developers, sysadmins and support engineers, having tools for observing what BPF programs are doing in the system is critical.
A lot has...
The PREEMPT_RT patchset is the longest existing large patchset living outside the Linux kernel. Over the years, the realtime developers had to maintain several stable kernel versions of the patchset. This talk will present the lessons learned from this experience, including workflow, tooling and release management that has proven over time to scale. The workflow deals with upstream changes...
There are two flavors of power management supported by the Linux kernel: system-wide PM based on transitions of the entire system into sleep states and working-state PM focused on controlling individual components when the system as a whole is working. PM-runtime is part of working-state PM concerned about the opportunity to put devices into low-power states when they are not in use.
Since...
Recent vulnerabilities like L1 Terminal Fault (L1TF) and Microarchitectural Data Sampling (MDS) have shown that the cpu hyper-threading architecture is very prone to leaking data with speculative execution attacks.
Address space separation is a proven technology to prevent side channel vulnerabilities when speculative execution attacks are used. It has, in particular, been successfully used...
Nowadays all consumer PC/laptop devices contain TPM2.0 security chip (due to Windows hardware requirements). Also servers and embedded devices increasingly carry these TPMs. It provides several security functions to the system and the user, such as smartcard-like secure keystore and key operations, secure secret storage, bruteforce-protected access control, etc.
These capabilities can be used...
Tools based on low level tracing tend to generate large amounts of data, typically outputted in some kind of text or binary format. On the other hand the predefined data analysis features of those tools are often useless when it comes to solving a nontrivial or very user-specific problem. This is when the possibility to make sophisticated analysis via scripting can be extremely useful.
Fast...
Linux is complex, and formal verification has been gaining more and more attention because independent "asserts" in the code can be ambiguous and not cover all the desired points. Formal models aim to avoid such problems of natural language, but the problem is that "formal modeling and verification" sound complex. Things have been changing.
What if I say it is possible to verify Linux...
The demand of DRAM across different platforms is increasing but the cost is not decreasing. Thus DRAM is a major factor of the total cost across all kinds of devices like mobile, desktop or servers. In this talk we will be presenting the work we are doing at Google, applicable to Android, Chrome OS and data center servers, on extracting more memory out of running applications without impacting...
Gen-Z Linux Sub-system
Discuss design choices for a Gen-Z kernel sub-system and the challenges of supporting the Gen-Z interconnect in Linux.
Gen-Z is a fabric interconnect that connects a broad range of devices from CPUs, memory, I/O, and switches to other computers and all of their devices. It scales from two components in an enclosure to an exascale mesh. The Gen-Z consortium has over...
