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Linux Systems [clear filter]
Monday, October 26
 

12:00 GMT

Evolution of Suspend-to-Idle Support in the Linux Kernel - Rafael Wysocki, Intel
Suspend-to-idle is a system-wide suspend variant which in principle does not rely on platform support. The suspend-to-idle control flow does not take non-boot CPUs offline and expects all CPUs to enter idle states through the idle loop, like in the working state of the system. However, it assumes that the scheduler tick will be stopped on all CPUs and the timekeeping will be suspended, which is a source of significant complications. It also expects system wakeup devices selected by user space to be functional and it needs to prevent all of the other interrupt sources from waking up the system. In some cases one interrupt source can signal both wakeup and non-wakeup events, so it is necessary to distinguish the former from the latter. All of that together causes the suspend-to-idle support code in the Linux kernel to be quite complex, especially on systems using ACPI, and that code has changed for multiple times in response to additional pieces of information on what is needed coming mostly from the users in the form of problem reports. I will describe the evolution of that code since its inception in 2013 and explain the reasons for making the changes in it.

Speakers
avatar for Rafael Wysocki

Rafael Wysocki

Software Engineer, Intel
Rafael maintains the Linux kernel’s power management infrastructure and the core ACPI support code. He works at Intel and focuses on the mainline Linux kernel development. Rafael has been actively contributing to Linux since 2005, in particular to the kernel’s suspend/hibernate... Read More →



Monday October 26, 2020 12:00 - 12:50 GMT
Linux Systems Theater
  Linux Systems, Power Management
 
Tuesday, October 27
 

18:30 GMT

The Fall of the Legacy - Vaibhav Gupta, Open Source Contributor
Power Management has always been a focal point in Linux, and along with PCI, it is like talking about fascinating powers subtle to handle. Among many ingredients of the magical PCI PM, PCI Core is a special one. The legacy framework provided good interaction between the Core and drivers, but a few years back, we came up with a generic approach that gave more control to the Core and made it possible for drivers to support PM without PCI helper functions. Vaibhav will discuss the simplification achieved after those unnecessary helper functions and the legacy support got removed as part of his project under the Linux Kernel Mentorship Program. He will talk about how this shift to the adoption of generic PM affects the performance and stability of PCI core functioning underneath. He will also discuss and share the work involved in converting drivers from legacy while balancing performance and stability along with changes to individual PCI drivers. You will come away with good knowledge of PCI PM and great respect for the community which has made it as performant as ever.

Speakers
avatar for Vaibhav Gupta

Vaibhav Gupta

Open-Source Contributor
Vaibhav Gupta is a senior year undergrad passionate about Kernel, Bootloader, Firmware, and any technology functioning closest to the hardware. He is an active contributor to Open-Source software. Recently, he worked on the Linux PCI Power-Management Framework under the Linux Kernel... Read More →



Tuesday October 27, 2020 18:30 - 19:20 GMT
Linux Systems Theater
  Linux Systems, Power Management
 
Wednesday, October 28
 

12:00 GMT

A Faster Hibernation/Resume Using Opportunistic Memory Reclaim - Andrea Righi, Canonical
Hibernation is usually considered as an obsolete feature for laptops, but it can still provide significant benefits in many different scenarios, if it can be made to work reliably and efficiently. The main bottleneck of hibernation is the cost of I/O, both at hibernation and resume time, but it is possible to reduce this cost using opportunistic memory reclaiming techniques. Canonical has been actively experimenting hibernation in cloud computing and virtualized environments. In the process we had the opportunity to experiment some improvements and learn surprising lessons. This session shares some technical details of the solutions that we developed, the lessons learned and the results that we found.

Speakers
avatar for Andrea Righi

Andrea Righi

Kernel Engineer, Canonical
Andrea Righi works for Canonical as a Kernel Engineer, focusing on performance analysis, tracing, virtualization technologies and power management topics. Andrea started working with the Linux kernel in 2004 while he was a student at the University. His contributions were mostly focused... Read More →



Wednesday October 28, 2020 12:00 - 12:50 GMT
Linux Systems Theater
  Linux Systems, Power Management
 

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