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Linux Plumbers [clear filter]
Wednesday, October 15
 

11:15am

Ftrace Kernel Hooks: More Than Just Tracing - Steven Rostedt, Red Hat
The function hook facility of ftrace is what makes ftrace stand out from other kernel tracers. The ability of live modification of the kernel to convert a nop into a ftrace callback has revolutionized tracing inside the kernel. Because it is dynamic, ftrace gives you the ability to chose what functions are to be traced, as well as tracing all functions within the kernel. This talk is not about tracing though, it is about what is coming in the future and the hurdles that needs to overcome and how it will be done. The ftrace function hooks allows for "hijacking" of a function. That is, when the function is called, the hook can intercept the call and divert it to call another function. Live patching such as kgraft and kpatch were built on this facility. To use these new features of ftrace, more must be done. This talk will go over how the hooks work and what more needs to be done.

Speakers
avatar for Steven Rostedt

Steven Rostedt

Principal Software Engineer, Red Hat Inc
Steven Rostedt works for Red Hat and is the main developer for their Real Time kernel. Steven is the maintainer of the Real-Time stable releases. He works upstream mainly developing and maintaining ftrace (the official tracer of the Linux kernel). He also maintains trace-cmd and kernelshark... Read More →


Wednesday October 15, 2014 11:15am - 12:05pm
Room 2

11:15am

Using Persistent Memory Effectively - Matthew Wilcox, Intel
Previous presentations on Persistent Memory have focused on the challenges that arise when providing raw access to the PM. This presentation focuses on the challenges facing user programs when they try to use PM. Matthew will review some of the difficulties in using mmaped storage (whether backed by PM or a regular file), and present some best practices and solutions included in the NVM Library.

Speakers
MW

Matthew Wilcox

Programmer, Oracle
Matthew works for Oracle on a variety of kernel projects. He has spoken at many Linux conferences on topics such as NVM Express, Persistent Memory and the XArray


Wednesday October 15, 2014 11:15am - 12:05pm
Room 8

12:15pm

ACPI And Device Trees - Friends Or Foes? - Rafael J. Wysocki, Intel OTC
ACPI was introduced when hardware compatibility with the IBM PC became insufficient to maintain the PC ecosystem. It allowed a single binary OS image to run on various platforms using the same CPU architecture, but not exactly hardware-compatible with one another. Today, Device Trees are used to address the same platform fragmentation problem in the ARM ecosystem. Of course, there are differences between ACPI and DT. Unlike DT, ACPI had a difficulty with passing arbitrary data to the OS, but that limitation is now being removed. With ACPI now able to provide the same data as DT, a need has arisen for a shared firmware-interface-agnostic specification of hardware properties. Similarly, the platform firmware interface access for device drivers in the OS should be unified, so the same driver can work equally well on systems with ACPI or DT. I will discuss work toward that goal in Linux.

Speakers
avatar for Rafael J. Wysocki

Rafael J. Wysocki

Software Engineer, Intel OTC
Rafael maintains the Linux kernel's core ACPI and power management code, including the core infrastructure for IO device PM, CPU PM and system suspend/hibernation. He works at Intel Open Source Technology Center as a Software Engineer focusing on the mainline Linux kernel. Rafael... Read More →


Wednesday October 15, 2014 12:15pm - 1:05pm
Room 8

12:15pm

Automatic NUMA Balancing - Rik van Riel, Red Hat
In NUMA systems, each CPU has its own bank of memory, resulting in fast access to local memory, and slower access to memory elsewhere in the system. Recently a mechanism has been implemented in the Linux kernel to automatically run programs near their memory, and to move memory to near the programs using it. This presentation explains why computers are built this way, why NUMA locality matters, how the automatic NUMA balancing kernel code works, what it can do, and what kind of performance improvements have been observed. This presentation is also a good opportunity to discuss recent and future developments for the automatic NUMA balancing code.

Speakers
RV

Rik Van Riel

Principal Software Engineer, Red Hat
Rik van Riel is a principal software engineer at Red Hat, and a long term contributor to the Linux kernel. He has contributed to the memory management subsystem, the scheduler, and various components related to virtualization. Rik is active in community projects like kernelnewbies.org... Read More →


Wednesday October 15, 2014 12:15pm - 1:05pm
Room 14

2:30pm

How to Design a Linux Kernel API - Michael Kerrisk, man7.org
The Linux kernel-user-space API is littered with design errors: APIs that are non-extensibe, unmaintainable, overly complex, limited-purpose, violations of standards, and inconsistent. Most of those mistakes can't be fixed because doing so would break the ABI that the kernel presents to user-space binaries. To further rub salt into the wound, kernel-user-space APIs are often buggy when first shipped.

Thus, it's important to get API designs right the first time. Taking (good and bad) examples from past APIs, I'll cover a number ideas on improving the design of future kernel user-space APIs. Those tips are relevant both for kernel developers producing the APIs and for user-space programmers looking at what kernel developers are serving to them. I'll also look at some strategies that developers can pursue in order to get help with improving the designs of APIs that they are producing.

Speakers
avatar for Michael Kerrisk

Michael Kerrisk

Trainer/consultant, man7.org Training and Consulting
Michael Kerrisk is the author of the acclaimed book, "The Linux Programming Interface" (http://man7.org/tlpi/), a guide and reference for system programming on Linux and UNIX. He contributes to the Linux kernel primarily via documentation, review, and testing of new kernel-user-space... Read More →


Wednesday October 15, 2014 2:30pm - 3:20pm
Room 14

2:30pm

Scaling Userspace @ Facebook - Ben Maurer, Facebook
Ben Maurer will discuss the server workloads that Facebook runs across its fleet. Ben will talk about work Facebook has done in various systems areas such as:

- Memory management: improvements we've made to memory allocation performance with jemalloc, reducing fragmentation in programs with large numbers of threads, and increasing performance with the use of NUMA.
- Synchronization: LifoSem -- a last, in first out semaphore built on top of futex
- Scheduling: using CPU queuing delay to measure capacity
- Networking: measuring network performance with TCP tracepoints.

Speakers
BM

Ben Maurer, Facebook

Facebook
Ben Maurer is the tech-lead of the Web Foundation team at Facebook. This team is responsible for managing the performance and reliability of Facebook's user facing infrastructure. Ben works at all layer's of Facebook's stack -- from javascript to the kernel. Ben joined Facebook in... Read More →


Wednesday October 15, 2014 2:30pm - 3:20pm
Room 8

3:30pm

First Glimpse at Shingled Drives - Hannes Reinecke, SUSE Labs
Recently storage vendors have advocated 'shingled media recording' devices. These drives are estimated to provide larger capacity than existing drives, but at the same time introduce a new access model. Hence it will not be possible to use them as all-purpose drives without modifications to the storage stack. For Linux there are two different proposals for handling these devices, either by using modified filesystems or by adding a device-mapper module.
This talk gives an overview about the technology behind shingled media recording and the proposed changes to the linux storage stack.
I will also present the results from running a modified stack on a pre-production device and its implications for further development.

Speakers
avatar for Hannes Reinecke

Hannes Reinecke

Teamlead Storage & Networking, SUSE Linux GmbH
Studied Physics with main focus image processing in Heidelberg from 1990 until 1997, followed by a PhD in Edinburgh 's Heriot-Watt University in 2000. Working at SUSE Labs with focus on storage and mainframe. Principal contact point for storage related issues on SLES and teamlead... Read More →


Wednesday October 15, 2014 3:30pm - 4:20pm
Room 14

3:30pm

Network Queuing is All Wet - Stephen Hemminger, Brocade
Why is my network slow? This is the most common user complaint in both
home and enterprise environments. Many of these problems are caused
by queuing problems in the network.

This talk will show some of the solutions developed, demonstrate how
they work, and identify where more work still needs to be done. The
demonstrations use the analogy of fluid dynamics to explain CoDel,
PIE, and other smart queuing mechanisms.

Speakers
avatar for Stephen Hemminger

Stephen Hemminger

Principal Engineer, Microsoft
Stephen has been actively involved with Linux kernel development for over 10 years. He has contributed several network device drivers, a network emulator, and is the maintainer of the bridging and iproute2utilities. After leaving LF, he went on to Vyatta (now acquired by Brocade... Read More →


Wednesday October 15, 2014 3:30pm - 4:20pm
Room 8

4:30pm

Linux Kernel Tinification - Josh Triplett, Intel
Cell phones and routers hardly qualify as "embedded" anymore; new embedded systems (or the new Things we will have an Internet Of) push for ever smaller storage and memory requirements. Most people building systems that small assume that Linux will not work for them, and that they have to use a dedicated embedded OS or custom code from scratch.

This talk will show just how small Linux can get while remaining functional, what it'll take to push Linux an order of magnitude smaller in the future, and how kernel and systems developers can avoid regressions in memory or storage requirements.

Speakers
avatar for Josh Triplett

Josh Triplett

Principal Engineer, Intel
Josh Triplett hacks on system software, including Rust, the Linux kernel, BITS, X, Git, Sparse, Debian, Chrome OS, and firmware. Josh enjoys using software for unconventional purposes, such as running Python in GRUB2 to test BIOS (https://biosbits.org). Josh has previously presented... Read More →


Wednesday October 15, 2014 4:30pm - 5:20pm
Room 2

4:30pm

Systematic Testing of Fault Handling Code in Linux Kernel - Alexey Khoroshilov, Russian Academy of Sciences
The talk presents a method to extend coverage of existing tests by systematic and targeted fault injection in Linux kernel. The method is developed within Linux File System Verification project that aims to provide an exhaustive test suite for Linux file system drivers.

The presented method of fault injection allows to systematically simulate faults dedicated to a file system driver under test (faults of memory allocation requests, bio layer, etc.). That means it does not introduce faults into requests coming from other modules and it implements systematic iteration of fault situations versus a prevailing random approach.

The talk presents results of experiments with the method, defines requirements to tests so they can be used with the method and discusses lessons learnt so far.

Speakers
avatar for Alexey Khoroshilov

Alexey Khoroshilov

Russian Academy of Sciences
Alexey Khoroshilov is a director of the Linux Verification Center of Institute for System Programming of the Russian Academy of Sciences. He has graduated from Computer Sciences Department of the Lomonosov's Moscow State University with honour and received a Ph.D. in Computer Sciences... Read More →


Wednesday October 15, 2014 4:30pm - 5:20pm
Room 8