Interactive applications, which includes everything from real time
games through flight simulators and virtual reality environments,
place strong real-time requirements on the whole computing environment
to ensure that the correct data are presented to the user at the
correct time. This requires two things; the first is that the time
when the information will be displayed be known to the...
Software that uses a 32-bit integer to represent seconds since the Unix epoch of Jan 1 1970 is affected by that variable overflowing on Jan 19 2038, often in a catastrophic way. Aside from most 32-bit binaries that use timestamps, this includes file systems (e.g. ext3 or xfs), file formats (e.g. cpio, utmp, core dumps), network protocols (e.g. nfs) and even hardware (e.g. real-time clocks or...
It is common to see Linux being used on real-time research projects. However, the assumptions made in papers are very often unrealistic. In contrast, researchers argue that the main metric used on PREEMPT RT, although useful, is an oversimplification of the problem.
It is a consensus that the academic research helps to improve Linux’s state-of-art, and vice-versa. So how can we reduce the gap...
The SCHED_DEADLINE scheduling policy is all but done. Even though it existed in mainline for several years, many features are yet to be implemented; some are already available as immature code, some others only exist as wishes.
In this talk Juri Lelli and Daniel Bristot De Oliveira will give the audience in-depth details of what’s missing, what’s under development and what might be desirable...
Historically, kernels that ran on Android devices have typically been 2+ years old compared to mainline (this year's flagship devices are shipping with 4.9 kernels) and because of the challenges associated with updating, most devices in the field are far behind the latest long-term stable (LTS) releases. The Android team has been gradually putting in place the necessary processes and...
Heterogeneous computing use massively parallel devices, such as GPU, to crunch through huge data-set. This talks intends to present the issues, challenges and problems related to memory management and heterogeneous computing. Issues and problems from one address space per device which makes exchanging or sharing data-set between devices and CPUs hard, complex and error prone.
Solutions...
The first rule of kernel maintenance is that there are no hard and fast rules. While there are several documents and guidelines on patch contribution, advice on how to serve in a maintainer role has historically been tribal knowledge. This organically grown state of affairs is both a source strength and a source of friction. It has served the community well to be adaptable to the different...
Containers (or Operating System based Virtualization) are an old
technology; however, the current excitement (and consequent
investment) around containers provides interesting avenues for
research on updating the way we build and manage container technology.
The most active area of research today, thanks to concerns raised by
groups supporting other types of virtualization, is in improving...
Using graphics cards for compute acceleration has been a major shift in technology lately, especially around AI/ML and HPC.
Until now the clear market leader has been the CUDA stack from NVIDIA, which is a closed source solution that runs on Linux. Open source applications like tensorflow (AI/ML) rely on this closed stack to utilise GPUs for acceleration.
Vendor aligned stacks such as AMD's...
Side channel attacks are here to stay. What can we do inside the operating system to proactively defend against them? This talk will walk through a few of the ideas that Intel’s Open Source Technology Center are developing to improve our resistance to side channel attacks as part of our new side channel defense project. We would also like to gather ideas from the rest of the community on what...
Plugging in USB sticks, building VM images, and unprivileged containers all give rise to a situation where users are mounting and dealing with filesystem images they have not built themselves, and don't necessarily want to trust.
This leads to the problem of how to mount and read/write those filesystems without opening yourself up to more risk than visiting a web page.
I will survey what has...
What could be done in the kernel to make strace happy.
Being a traditional tool with a long history, strace has been making every effort to overcome various deficiencies in the kernel API. Unfortunately, some of these workarounds are fragile, and in some cases no workaround is possible. In this talk maintainers of strace will describe...
Formal methods have a reputation of being difficult, accessible mostly to academics and of little use to the typical kernel hacker. This talk aims to show how, without "formal" training, one can use such tools for the benefit of the Linux kernel. It will introduce a few formal models that helped find actual bugs in the Linux kernel and start a discussion around future uses from modelling...
Providing a consistent and predictable performance experience for applications is an important goal for cloud providers. Creating isolated job domains in a multi-tenant shared environment can be extremely challenging. At Google, performance isolation challenges due to memory bandwidth has been on the rise with newer workloads. This talk covers our attempt to understand and mitigate isolation...
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. In this talk, Daniel Xu will cover why the Linux kernel OOM killer is surprisingly ineffective and how oomd, a newly opensourced userspace OOM killer, does a more effective and reliable job. Not only does the...
The physical memory management in the Linux kernel is mostly based on single page allocations, but there are many situations where a larger physically continuous memory needs to be allocated. Some are for the benefit of userspace (e.g. huge pages), others for better performance in the kernel (SLAB/SLUB, networking, and others).
Making sure that contiguous physical memory is available for...
WireGuard [1] [2] is a new network tunneling mechanism written for
Linux, which, after three years of development, is nearly ready for
upstream. It uses a formally proven cryptographic protocol, custom
tailored for the Linux kernel, and has already seen very widespread
deployment, in everything from smart phones to massive data center
clusters. WireGuard uses a novel timer mechanism to hide...
Lockdep (the deadlock detector in the Linux kernel) is a powerful tool to detect deadlocks, and has been used for a long time by kernel developers. However, when comes to read/write lock deadlock detections, lockdep only has limited support. Another thing makes this limited support worse is some...
Most modern microprocessors employ complex instruction execution pipelines such that many instructions can be 'in flight' at any given point in time. The efficiency of this pipelining is typically measured in how many instructions get completed per CPU cycle and the metric gets variously called as Instructions Per Cycle (IPC) or the inverse metric Cycles Per Instruction (CPI). Various factors...
Over the past few years the graphics subsystem has been spearheading experiments in running things differently: Pre-merge CI wrapped around mailing lists using patchwork, committer model as a form of group maintainership on steroids, and other things. As a result the graphics people have run into some interesting new corner cases of the kernel's "patches carved on stone tablets" process.
On...
The Google computing infrastructure uses containers to manage millions of simultaneously running jobs in data centers worldwide. Although the applications are container aware and are designed to be resilient to failures, evictions due to resource contention and scheduled maintenance events can reduce overall efficiency due to the time required to rebuild complex application state. This talk...
The eXpress Data Path (XDP) has been gradually integrated into the Linux kernel over several releases. XDP offers fast and programmable packet processing in kernel context. The operating system kernel itself provides a safe execution environment for custom packet processing applications, in form of eBPF programs, executed in device driver context. XDP provides a fully integrated solution...
