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Joseph Salisbury (Maintainer of v5.15-rt real-time patchset)18/09/2024, 10:00
Maintaining A Stable Real-time Kernel Patchset
josephtsalisbury@gmail.com
jsalisbury@kernel.orgAbstract:
The Real Time Linux collaborative project coordinates the maintenance and hosts the repositories for the PREEMPT_RT patchset[0]. This patchset provides the logic for changing a generic vanilla kernel into a real-time operating system.The real-time patchset is developed in...
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Julia Lawall (Inria)18/09/2024, 10:45
Program verification, ie, producing a proof that code matches its specification, can be seen as the ultimate form of bug finding. Nevertheless, program verification is widely considered to be difficult and time consuming. Furthermore, in the case of the Linux kernel, any verification effort is likely quickly out of date, given the rate of change in the code base. Still, it is not necessarily...
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Tomas Glozar (Red Hat)18/09/2024, 12:00
Calling sleeping locks in a non-preemptible context is not allowed because it causes a "BUG: scheduling while atomic" error. This problem is particularly relevant for PREEMPT_RT kernels, which convert all spin locks into sleeping locks. As a result, unexpected scheduling can occur in non-preemptible contexts. One way to detect this issue is by annotating such sleeping functions with...
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Javier Gonzalez (Samsung Electronics)18/09/2024, 12:45
Data Placement has been one of major the sources of innovation in storage. Specifically in NAND Memory, technologies such as Open-Channel SSDs, Key-Value SSDs, Multi Stream, Zoned Namespaces (ZNS), and lately Flexible Data Placement (FDP) have attempted at covering different use-cases. While there is overlap among several of these technologies, they exhibit significant differences when it...
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Pratyush Yadav18/09/2024, 15:00
Applications with large in-memory caches like databases or storage nodes suffer
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heavily from downtime when upgrading the kernel. They need to go out of
commission not only for the reboot time, but also for the time it takes to warm
up the caches again. This talk proposes a mechanism that allows handing over
userspace memory to the next kernel after a kexec. This allows such... -
Fam Zheng18/09/2024, 15:45
It is critical to boot the kexec kernel fast in the system live-update scenarios. As one challenge in this case, a kexec procedure today always initializes ACPI in the same way as a cold reboot, which can take more than 100ms on latest x86 servers. Most of the time is spent on table loading, interpreting and finding idle states, which practically won't have changing side effects across a kexec...
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Helen Koike (Collabora), Nikolai Kondrashov (Red Hat), Tales da Aparecida (Red Hat)18/09/2024, 17:00
The email workflow brought the kernel to life, saw it through immense growth, and into widespread popularity. However, it seems to be reaching its limits, prompting Linus to say we need to "find ways to get away from the email patch model" to make maintainer life easier.
Kernel workflow evolution (1991 - start, 2002 - BitKeeper, 2005 - Git, 2008 - Patchwork) seems to have stopped fifteen...
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Boqun Feng (Microsoft), Neeraj Upadhyay (AMD), Paul McKenney (Meta)18/09/2024, 17:45
Reference counting in Linux kernel is often implemented using
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conditional atomic increment/decrement operations on a counter. These
atomic operations can become a scalability bottleneck with increasing
numbers of CPUs. The RCURef patch series [1] and Nginx refcount
scalability issues [2] are recent examples where the refcount bottleneck
significantly degraded application... -
Gustavo A. R. Silva (The Linux Foundation)19/09/2024, 10:00
The introduction of the new -Wflex-array-member-not-at-end compiler option, released in GCC-14, has revealed approximately 60,000 warnings in the Linux kernel. Among them, some legitimate bugs have been uncovered.
In this presentation, we will explore in detail the different strategies we are employing to resolve all these warnings. These methods have already helped us resolve about 30% of...
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Wentao Zhang (University of Illinois Urbana-Champaign), Tingxu Ren (University of Illinois at Urbana-Champaign), Jinghao Jia (University of Illinois Urbana-Champaign), Darko Marinov (University of Illinois at Urbana-Champaign), Tianyin Xu (University of Illinois at Urbana-Champaign)19/09/2024, 10:45
Modified condition/decision coverage (MC/DC) is a fine-grained code coverage
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metric required by many safety-critical industrial standards, including
aerospace, automotive, medical and rail. It is challenging to measure MC/DC of
targets as complex as Linux kernel. We will discuss our effort on measuring
MC/DC of Linux and the opportunities it would open up. The main challenges... -
Don Zickus (Red Hat), Gustavo Padovan (Collabora)19/09/2024, 12:00
KernelCI started 10 years ago as a small project to test the kernel on Arm devices. The project grew over the years and today a new architecture is in place. In this talk, Don and Gustavo will present you the new KernelCI. The KernelCI community put a lot of effort recently to design and implement its new testing architecture with a focus on facilitating the kernel community and industry...
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Luigi Pellecchia19/09/2024, 12:45
How to track existing LTP tests for a set of syscalls to their man pages and spot gaps?
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How can the community be notified by a change to the kernel source code or to the man page?
How to provide a Test environment that is integrated in an automated CI workflow?
We'll discuss how BASIL can answers some of these questions. -
19. Addressing Duplicated Symbol Names in kallsyms: Introducing kas_alias for Symbol DifferentiationAlessandro Carminati19/09/2024, 15:00
Duplicated symbol names in
Go to contribution pagekallsymspose challenges for tracing and probing operations in the Linux kernel environment, complicating system observability and debugging.
To tackle this issue,kas_aliasis introduced, a new tool added to the kernel build process to identify duplicated symbols and add aliases to them, ensuring existing workflows remain unaltered.
kas_aliasoperates on... -
Eduardo Vela Nava (elgooG), Space Meyer (1e100)19/09/2024, 15:45
Some kernel mitigations are very expensive, some others fail to adequately address classes of vulnerabilities. At the same time it is hard for users to make informed cost/benefit decisions about whether to enable a particular mitigation or not.
This presentation critically assesses a handful of past and upcoming security mitigations, proposing a data-driven evaluation of their impact on...
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Saravana Kannan19/09/2024, 17:00
Device links have been around for a while now, but not used extensively/effectively until fw_devlink was implemented and improved over the last few years. fw_devlink is finally in a fairly stable state where it can correctly handle cyclic dependencies and also break the cycle.
With all the additional device dependency tracking info that's available in the kernel, the community can improve...
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Parthiban N (Linumiz)19/09/2024, 17:45
Embedded System-on-Chips (SoCs) provide unique, device-specific keys for encrypting and decrypting user data, serving as a Root of Trust (ROT) store crucial for security. Historically, the Trusted Keys framework in the Linux Kernel was tightly integrated with Trusted Platform Module (TPM), limiting the ability to incorporate additional sources of trust like Trusted Execution Environments...
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Juri Lelli (Red Hat), Peter Zijlstra (Intel OTC), Steven Rostedt, Thomas Gleixner19/09/2024, 18:30
I would like to propose a BoF in honor of Daniel Bristot de Oliveira. I'd like it to be held on Thursday night after the last session, so that all can attend. I may even look to see if it is possible to serve refreshments (beer and wine), that would be paid for by those willing to donate. People would be able to come up and give stories about their memories of Daniel. The purpose of this BoF...
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Mathieu Desnoyers (EfficiOS Inc.)20/09/2024, 10:00
Introduce the librseq per-CPU user-space memory allocator. It implements concepts similar to the Linux kernel percpu allocator in userspace, and thus reduces waste of per-CPU data structures hot cache lines by eliminating padding usually required to eliminate false-sharing, and in addition tackles issues that arise from resident memory waste when restricting processes with scheduler affinity...
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Byungchul Park20/09/2024, 10:45
A new mechanism, LUF(Lazy Unmap Flush), defers tlb flush until folios that have been unmapped and freed, eventually get allocated again. It's safe for folios that had been mapped read-only and were unmapped, as long as the contents of the folios don't change while staying in pcp or buddy so we can still read the data through the stale tlb entries.
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... -
Khasim Syed Mohammed20/09/2024, 12:00
While Car Audio is a commoditized technology, it’s still one of the sought after research area in automotive infotainment. The technology advancement in semiconductor technology has helped in integrating large IPs like DSPs, accelerators, analytics engines, etc into one single SOC, they have definitely resolved the requirement of low power, low cost, high performance requirements. But, the...
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Jan Kara20/09/2024, 12:45
Fanotify is the filesystem notification framework in Linux. In recent years it has gained substantial amount of new features. In this talk we will survey developments in fanotify such as filesystem notification marks, reporting of directory events, support for unpriviledged users, marks that can be evicted in case of memory pressure, and others. In the end we will also outline features...
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Joel Fernandes, Mr Vineeth Remanan Pillai (Google)20/09/2024, 15:00
Double scheduling is a concern with virtualization hosts where the host schedules vcpus without knowing whats run by the vcpu and guest schedules tasks without knowing where the vcpu is physically running. This causes issues related to latencies, power consumption, resource utilization
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etc. An ideal solution would be to have a cooperative scheduling framework where the guest and host shares... -
Olivier Singla (Ampere Computing), Yang Shi (Ampere Computing)20/09/2024, 15:45
The Linux kernel has supported multi-sized THP since v6.8 allowing the use of intermediate sized huge pages less than 2M. ARM64 supports contiguous PTEs where multiple PTE entries can be coalesced one TLB entry. This will increase the size of memory covered by the TLB entries and avoid page table walks to create TLB entries.
We ran a series of benchmarks on Ampere Altra using some popular...
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Hari Bathini (IBM)20/09/2024, 17:00
On almost all architectures, kdump has been the default or the only mechanism,
to capture vmcore - used for debugging kernel crashes, for close to couple of
decades. Fadump (Firmware-Assisted Dump [1], pronounced F-A-Dump) is being used
as the alternative dump capturing mechanism on ppc64, for over a decade.This talk gives a brief introduction of kdump, why fadump was introduced...
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Andrea Righi (NVIDIA)20/09/2024, 17:45
In the realm of operating systems, the heart of performance lies in the CPU scheduler: a critical component responsible for managing the execution of tasks on a system.
Traditionally, delving into CPU scheduling policies was largely confined to a small group of experienced kernel developers. Yet, there is an increasing aspiration to democratize this domain, facilitating experimentation and...
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