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.

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.

Lessons not Learned - Continuing Latency Issues in Linux

We still have wonderful fsync offenders. Look at Kopete for example, or at Chrome. You don't want to be running that on battery or in a low latency environment:

Process kopete (1868)            Total: 19098.1 msec

fsync() on a file        6008.6 msec    99.8 %

Scheduler: waiting for cpu   19.4 msec  0.2 %

Or Iron (a privacy-enhanced Chrome/Chromium browser)

Process iron (5822)  Total: 13753.6 msec
fsync() on a file           5090.9 msec   70.3 %
Writing a page to disk 1412.8 msec 10.3 %
synchronous write         524.5 msec  3.8 %

If you use ext4, you can add some of these mount options to decrease the latency impact. But this decreases data security:
noatime,nodiratime,nobh,barrier=0,commit=100,data=writeback