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. 😛

Don’t you hate it when you go into one of your git repos to do some updates, and realized you have a large diff of uncommitted code of a work in progress that you left and forgot about! 😛

I just realized. The more you comment your code and make it understandable, the easier it is for other people to takeover and rewrite your code. This means that when you retire/pass-away, your code will likely be quickly overwritten and your legacy gone from the active code base.

So, if you write complex clever code with little to no documentation, your code is more likely to be immortalized in the code base as everyone will be too afraid to touch it and possibly break it.

I thought of this when looking into the Linux TTY code base

I wasn't a speaker at Embedded Recipes this year but I still pulled off my obligatory selfie with the ER speakers.

Traditional mandates all ftrace talks must start with a selfie from a camera and not a phone! At #kr2023

Paul McKenney using toilet paper to describe latency of CPUs

My obligatory selfie at Kernel Recipes

The conference will start soone. You can follow it here:

https://www.youtube.com/watch?v=PSS9VemnSkg

Enjoy!

Linux Plumbers Conference General Registration has reopened. Get your tickets now before we sell out again.

https://lpc.events/blog/current/index.php/2023/09/23/linux-plumbers-conference-general-registration-reopened/

Finished the content of my #kr2023 presentation. Now I just need to touch it up, but that can be done later.