Meetup #21: The Kexec meetup: Linux Kernel Debugging and booting Mechanisms

Welcome to our 21st (published) meetup, (re)tackling Linux Kernel debugging and booting mechanisms after 5 years (and videos on youtube that are still good, and are said to have inspired a generation, heh).
This meetup up will have a special community take, and we will both discuss kexec mechanisms (For faster booting, and postmortem debugging), and subtly implement kexec-like mechanism on the Israeli Linux kernel community. Embedded developers - don't feel outsiders. If you are interested in the Linux kernel, you are guaranteed to pick up a thing or 12, and if you are not, well, you better be, and dozens of hours of hardcore Linux kernel contents are waiting for you in our youtube channel, to make you worthy of attending the next Linux kernel meetups!

Double registration alert:
Registration is mandatory and *will be checked* so please make sure you RSVP here, and in addition register in https://docs.google.com/forms/d/e/1FAIpQLSf8X2YvLD8dTTDowQXb1Q_Xn2_LvRWZN_3WvSOaSQKqUatjiA/viewform?usp=sharing
You absolutely have to register in this link, and carefully read the event guidelines there. It is IMPORTANT and we want you, by all means, to avoid any inconveniences (due to being lazy and not reading CAREFULLY what we wrote),
Don't lie, don't write partial details, don't play games, and don't pretend you are oh-so-secret. You are not. If you really think you are, and plan to attend, reach out to Ron in private, and he will make that decision for you.

AGENDA

17:30PM - 6:00PM Gathering. Networking, High Fives, Hugs (Everyone @ Embedded Israel)

6:00PM - 6:10PM Welcome notes: About our hosts, Embedded Israel, KernelIl and the reincarnation of KernelTLV - community Building #1 - Ron Munitz (Organizer, Embedded Israel, what used to be KernelTLV)

6:10PM - 6:45PM Kernel Debugging mechanisms: Postmortem debugging with kexec kdump and friends - Ron Munitz (CoE @ The PSCG/PSCG Holdings LTD)
Following our hours of recorded contents on kernel debugging mechanisms (videos #12-#29 in the youtube playlist , as well as some more videos later on, maybe earlier, and quite a few unrecorded talks), we will quickly remind those who forgot, and those who have never seen them, what are some of the things that we covered, and how to navigate the playlist. Since the QEMU hardware debugger, KDB and KGDB got a lot of attention back then, they will not be discussed this time other than this short refresher.

What we will be discussing is postmortem debugging by introducing you to linux core dumps and the tools to inpsect them, both on a live image (/proc/kcore and on a postmortem core dump, "vmcore". While doing so, we will cover some of of the internals of sysrq-magic which is a wonderful debug mechanism, and the panic() function (if there is demand, additional lectures will come that take a deeper cut in them).

The talk is built in a way that should be interesting and teach a thing or two experienced kernel developers, and still, teaches some foundation, and gives the methods for new comers to reproduce the steps given in it, and teach themselves how stuff works, impressing themselves with their new found knowledge, in their way to show off their skills as the lecturers in a few months or years from now.

6:45PM - 7:00PM - Networking Break
7:00PM - 7:40PM State persistence over kexec - Mike Rapoport (Linux Kernel Engineer @ Microsoft)
For long time kexec was a faster way to reboot a machine without incurring delays caused by firmware and bootloaders. However for many applications even a kexec reboot still means significant service degradation, like disruption of the running guests in virtualized environments and the need to rebuild in-memory caches for large databases.

We propose Kexec HandOver (KHO) mechanism that allows serialization and deserialization of kernel data as well as preserving arbitrary memory ranges across kexec.

In addition, KHO keeps physically contiguous memory regions that are guaranteed to not have any memory that KHO would preserve, but still can be used by the system. The kexeced kernel bootstraps itself using those regions and marks all handed over memory as in use. KHO users then can recover their state from the preserved data. This includes memory reservations, where the user can either discard or claim reservations.

7:40PM - 8:00PM Community Building For those who really want to have a community / networking for those who came for free food
This is a place for those who want to be involved, and take part in the decisions going forward. It is also the place to plan the next meetups, including, starting and finalizing the agenda while we meet (And that is possible, if good and serious people attend)

8:00PM - Until we are kicked out Community Building / Lightning Talks / Networking

We are looking forward to seeing you, and having more people participate. As (almost) always, if you have something great to talk about - I am happy to "give up my spot" for you. And by all means, submit talks. Submit Lightning talks. Participate. Share the word. Have your organization sponsor the community - we are planning awesome things, and we want to always keep objective!

Last words: Everyone, including everyone registers. No one unsubscribes from updates. Please don't test us.

See you soon!