With my new persistent memory mapped ring buffer, were I can retrieve the tracing buffer from the previous boot that crashed, I was able to debug a recent issue. To do this, I added code to allow trace_printk() to be directed to the persistent ring buffer, along with enabling the printk console trace event (writes all printk()s to the tracing ring buffer), I was able to get the perfect idea of what was happening that lead up to the crash!

https://lore.kernel.org/lkml/20240823013902.135036960@goodmis.org/

ANNOUNCE Just released:

trace-cmd v3.3 and libtracecmd 1.5.2

libtracefs v1.8.1

libtraceevent v1.8.3

A tribute to Daniel Bristot de Oliveira from Linux Plumbers. https://lpc.events/blog/current/index.php/2024/07/06/in-memory-of-daniel-bristot-de-oliveira/

Daniel Bristot de Oliveira passed away on Monday, June 24th at the age of 37. Another sad loss for the Linux kernel developer community, Daniel will be sorely missed.

In memory of Daniel: https://t.co/kQCQyTCo1a

Mourning Daniel Bristot de Oliveira

https://lwn.net/Articles/979912/ #LWN

https://lwn.net/Articles/979912/

"And you get a scheduler, and you get a scheduler, and you get a scheduler"

[ stolen from a colleague ]

Linus Torvalds: And for everybody else as a "It's happening" heads-up.

Linux Plumbers 2024 has accepted 9 Microconferences! But we had 26 submissions for 18 slots! What to do with that? Read about it here: https://lpc.events/blog/current/index.php/2024/05/03/awesome-amount-of-microconference-submissions/

Just posted a proof of concept that allows you to read a trace after a reboot, including a kernel crash!
https://lore.kernel.org/lkml/20240306015910.766510873@goodmis.org/

Doing some testing against a change; I ran two traces. Recording the trace before applying the patch as trace-b.dat and then calling the trace file after applying the patch as trace-a.dat. Then doing an ls trace*.dat I have:

trace-a.dat
trace-b.dat

And it looks like trace-a.dat should come before trace-b.dat. I’m so confused! 😛

Looks like a lot of people are still without power in Portland. Linus gets a surprise vacation during the merge window 🫤

I’m being “schooled” by Al Viro on how dcache, inodes, and files work internally.

This is a very interesting read that I recommend anyone that wants to understand VFS better should look at.

And don’t just stop at that email, the thread goes on. Very educational. Hopefully someone smarter than I can add this to the VFS documentation in the kernel 😉

Allow ring buffer to have bigger sub buffers

Hmm, that subject line may not have been appropriate. 🤔

I don’t mind clean up patches, but this is the reason a lot of Linux kernel maintainers frown on them.

https://lore.kernel.org/all/2023120938-unclamped-fleshy-688e@gregkh/

This failure is because of a clean up patch that converted everything to “bool” where it could be:

https://lore.kernel.org/all/20230305155532.5549-3-ubizjak@gmail.com/T/#u

If I had not accepted that clean up, this backport would have been pulled in automatically with no extra work from myself. But because I added that clean up, I now have to fix this for every stable release before that clean up 🙁

I really hate grub2. Now they hide the menu entries in a separate directory. This really makes it difficult when testing kernels and adding tweaks to the command line. It now doesn’t seem to find my test kernel and I have no idea how to make it do so. 😠

It’s the month of December. Do you know what that means? It means it’s time to run my workstation and server with branch tracing enabled! https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/compiler.h#n50

[$] Deferred scheduling for user-space critical sections https://lwn.net/Articles/948870/ #LWN

OK, I just upgraded my baremetal machine from Fedora 33 to Fedora 38 (by stepping through 35 and 37 as in between steps). I haven’t used this machine in a long time as I now do most of my testing with VMs. But I’m doing some performance testing that I wanted to know baremetal numbers.

WTF Fedora! 38 introduced a “suspend in 15 minutes if not logged in”. It doesn’t care if you are ssh’ed in or not! What’s worse is that this machine isn’t even hooked to a monitor (serial console only).

Luckily, I found a link that shows me how to disable that. 😛