LWN: Comments on "Ftrace: The hidden light switch"

Ftrace: The hidden light switch

ituralde — Tue, 03 Mar 2015 09:24:24 +0000

Is it possible to use perf-tools (or merely ftrace of perf_events) to profile functions of kernel modules? By modules I mean once that are inserted to a stable kernel.
The Q might be silly, I am quite a novice in this matter.

Ftrace: The hidden light switch

bgregg — Fri, 12 Sep 2014 06:45:34 +0000

I'd like to write a comparative article at some point, although it is challenging to compare them all, since there's so many factors to take into account. And I'd like to do more research first, such as using SystemTap's non-debuginfo features more (which are practically undocumented, but should be an important factor for real world usage), spend more time with LTTng, try out the ftrace function triggers, try writing a kernel module for tracing based on samples/kprobes/*.c (has no one done this? I can find zero examples other than the kernel source), etc.

The best place for tracing system comparisons has, historically, been here on lwn.net, like the ktap vs eBPF article, and others by Jonathan Corbet. So, keep reading... :-)

Ftrace: The hidden light switch

Shugyousha — Mon, 25 Aug 2014 09:11:48 +0000

A great article indeed.

There is a lot of tracing infrastructure in the Kernel and a lot of tools for tracing available. It would be nice if we could get an(other?) article comparing the different tools and their capabilities. Candidates for such a comparison would be SystemTap, ktap, eBPF, the Kernel perf tool and maybe the newer sysdig (http://www.sysdig.org/) for example.

Ftrace: The hidden light switch

bernat — Sun, 17 Aug 2014 19:45:24 +0000

Great article!

Unfortunately, unlike Ubuntu kernels, Debian kernels come with most useful tracers disabled. This seems due to this bug:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=568025

I have opened a bug report to ask for them to be enabled again:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=758469

With the fact that Debian does not come with debug symbols for all packages (something that I hope to address in the future), this makes Debian a bit more unfriendly with respect to all those performance tools, compared to Ubuntu.