Kernel Shark (trace-cmd/ftrace GUI) presentation by Steve Rostedt

There's a nice (WebM) video of Steve presenting the gui to trace-cmd and it's output of ftrace's work.

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Ftrace Favorites Cheat Sheet - Fun Commands to Try with Ftrace

When you see the ftrace presentation or read through the presentations, you get an overload. It's just too much at once. That's why I decided to write up this little cheat sheet for ftrace with commands from Steve's presentations.

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Checking if at least a Kernel Version is Runnig in Bash

kernelatleast() { # provide number like 2639

kver=$(uname -r|cut -d\- -f1|tr -d '.'| tr -d '[A-Z][a-z]')

kver=${kver:0:4}

if [ $1 -ge $kver ] ; then

return 0;

else

return 1;

fi

}

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Getting the Right Kernel Configuration for Your System the Easy Way

If you're lazy (and/or smart), you still want to compile a kernel for your system and save the time compiling all the things you don't need, then make localmodconfig is your friend. It will create a .config from the modules you have loaded, as Christoph Hellwig did not fail to mention repeatedly at the LinuxTag. But there are two caveats.

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Using a Linux Driver for a Device that is not yet supported without recompiling

If you have  a new shiny webcam or some other device you want to use in Linux, here is a quick short guide how you can have it runnig within minutes with a bit of luck.

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Why Not Scale the CPU on Schedule?

Usually e.g. CPU frequency scaling works mostly by seeing how much of the CPU is utilized and then reacting by setting the frequency to a certain level to satisfy this need. But why not at least in addition introduce an interface for some software, e.g. media players, to inform the kernel up front how much CPU it will need. Then it the CPU will be available on time.

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The Linux Kernel Trojan Horse Gift

Linus describes how he prefers new features to be introduced to Linux:

In other words, every new crazy feature should be hidden in a nice solid "Trojan Horse" gift: something that looks _obviously_ good at first sight.

The fact that it may contain the germs for future features should be hidden so well that not only is it not used as an argument ("Hey, look at all those soldiers in that horse, imagine what you could do with them"), it should also not be obvious from the source code ("Look at all those hooks I sprinkled around, which aren't actually used by anything, but just imagine what you could do with them").
Linus

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New Open Source Poulsbo Driver in 2.6.39 staging

It works pretty nicely - though just as a framebuffer device so far. A specialized Xorg userspace driver for the new staging kernel driver is expected sometime soon. It already supplies KMS and can be used with the fbdev driver of Xorg. So next time you want to try a new kernel you can at least get into a working X without much ado. And there will surely be at least a simple driver coming with new kernels now. The first steps have been taken. And of course, all this is hopefully just the beginning...

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More Latency Tweaks for Desktop Users

For those of you who got hooked already by the magical kernel patch that went into 2.6.38 and seriously improved latency with high load, there is a special daemon now that takes it further: uLatencyD. And for the lazy Ubuntu people there is a ppa available, too:
sudo apt-add-repository ppa:poelzi/ulatencyd-stable
sudo apt-get update
sudo apt-get install ulatencyd

It works immediately and in my experience so far: veeery nice.

Enjoy.

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What can Governor Adjustments do for your Battery Mileage?

After my previous post about Android saving power with Linux governor tweaking, I did some governor tweak testing on my netbook with a tweaked phoronix test suide (pts) and came up with these results:

The first two show the power usage in Watts, the third shows the frequencies used during the test.

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Immediate Latency Improvement on Recent Linux Kernels

Check out this article on Webupd8. But I'm sure an easier version you can just install as a normal package will come out soon as well.

But it works excellently indeed. I can transcode now and I don't even notice any change in responsiveness.

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Disabling Fsync in Laptop_Mode

There are several libraries that help you to disable fsync temporarily so your hard disk doesn't always spin up to save your notebooks battery. Of course that is not very flexible as you need to preload the libraries meaning you have to restart the programs.

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