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Daniel Xu (Facebook)09/09/2019, 10:00
Running out of memory on a host is a particularly nasty scenario. In the Linux kernel, if memory is being overcommitted, it results in the kernel out-of-memory (OOM) killer kicking in. Perhaps surprisingly, the kernel does not often handle this well. oomd builds on top of recent kernel development to effectively implement OOM killing in userspace. This results in a faster, more predictable,...
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Julien Desfossez (DigitalOcean), Vineeth Remanan Pillai09/09/2019, 10:45
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...
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Rohit Jnagal, Stephane Eranian (Google Inc), Ian Rogers (Google Inc)09/09/2019, 12:00
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...
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John Ogness (Linutronix GmbH)09/09/2019, 12:45
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...
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Matthew Garrett (Google)09/09/2019, 15:00
TPM remote attestation (a mechanism allowing remote sites to ask a computer to prove what software it booted) was an object of fear in the open source community in the 2000s, a potential existential threat to Linux's ability to interact with the free internet. These concerns have largely not been realised, and now there's increasing interest in ways we can use remote attestation to improve...
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Mr Feng Tang09/09/2019, 15:45
Linux kernel fastboot is critical for all kinds of platforms: from embedded/smartphone to desktop/cloud, and it has been hugely improved over years. But, is it all done? Not yet!
This topic will first share the optimizations done for our platform, which cut the kernel (inside a VM) bootime from 3000ms to 300ms, and then list the future potential optimization points.
Here are our...
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Nikolai Kondrashov (Red Hat), Veronika Kabatova (Red Hat)09/09/2019, 17:00
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...
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Mr Jason Gunthorpe (Mellanox Technologies)09/09/2019, 17:45
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...
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Arnaldo Carvalho de Melo (Red Hat Inc.)10/09/2019, 10:00
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...
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Daniel Wagner, Daniel Bristot de Oliveira (Red Hat, Inc.), Steven Rostedt, Tom Zanussi, John Kacur10/09/2019, 10:45
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...
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Rafael Wysocki (Intel Open Source Technology Center)10/09/2019, 12:00
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...
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Alexandre Chartre (Oracle), James Bottomley (IBM), Mike Rapoport (IBM), Joel Nider (IBM Research)10/09/2019, 12:45
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...
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Mr Andreas Fuchs (Fraunhofer SIT)10/09/2019, 15:00
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...
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Yordan Karadzhov (VMware)10/09/2019, 15:45
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...
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Rik van Riel (Facebook)10/09/2019, 17:00
The cgroups CPU controller in the Linux scheduler is implemented using hierarchical runqueues, which introduces a lot of complexity, and incurs a large overhead with frequently scheduling workloads. This presentation is about a new design for the cgroups CPU controller, which uses just one runqueue, and instead scales the vruntime by the inverse of the task priority. The goal is to make people...
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Daniel Bristot de Oliveira (Red Hat, Inc.)10/09/2019, 17:45
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...
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Shakeel Butt (Google), Suren Baghdasaryan (Google), Yu Zhao (Google)11/09/2019, 10:00
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...
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Jim Hull (Hewlett Packard Enterprise), Betty Dall (HPE), Keith Packard (Hewlett Packard Enterprise)11/09/2019, 10:45
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...
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Mr Christian Brauner11/09/2019, 12:00
Traditionally processes are identified globally via process identifiers (PIDs). Due to how pid allocation works the kernel is free to recycle PIDs once a process has been reaped. As such, PIDs do not allow another process to maintain a private, stable reference on a process. On systems under pressure it is thus possible that a PID is recycled without other (non-parent) processes being aware of...
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Jerome Glisse (Red Hat)11/09/2019, 12:45
With heterogeneous computing, program's data (range of virtual addresses) have to move to different physical memory during the lifetime of an application to keep it local to compute unit (CPU, GPU, FPGA, ...). NUMA have been the model used so far but it has assumptions that do not work with all the memory type we now have. This presentation will explore the various types of memory and how we...
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Mr Waiman Long (Red Hat)11/09/2019, 15:00
The most commonly used simple locking functions provided by the pthread library are pthread_mutex and pthread_rwlock. They are sleeping locks and so do suffer from unpredictable wakeup latency limiting locking throughput.
Userspace spinning locks can potentially offer better locking throughput, but they also suffer other drawbacks like lock holder preemption which will waste valuable CPU...
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Ben Widawsky
FPGAs are becoming more pervasive because they've gone down in price, and process improvements allow substantial designs to fit on commoditized hardware. Furthermore, processors are shipping with embedded FPGAs, making it an interesting target for scaled deployments and hobbyists alike. It's likely that in the foreseeable future, many platforms you use daily will have an FPGA embedded. As...
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Ben Widawsky
FPGAs are becoming more pervasive because they've gone down in price, and process improvements allow substantial designs to fit on commoditized hardware. Furthermore, processors are shipping with embedded FPGAs, making it an interesting target for scaled deployments and hobbyists alike. It's likely that in the foreseeable future, many platforms you use daily will have an FPGA embedded. As...
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