Re: [Bug #12208] uml is very slow on 2.6.28 host

Ingo Molnar
2008-12-18T14:37:52Z

* Mike Galbraith <efault-Mmb7MZpHnFY@public.gmane.org> wrote:

> On Tue, 2008-12-16 at 16:27 +0100, Miklos Szeredi wrote:
>
> > Is there a way to trace what is happening in the scheduler?
>
> Sure. Ingo has a script for gathering info (attached), if you run it,
> please gzip up the output and send me a copy offline to eyeball.
>
> There's also ftrace, but I've not tried that yet, so can't offer any
> advice, I use primitive but effective time_after() + printk() with klogd
> wakeup disabled (deadlock).

btw., there's a recent commit:

32a7600: printk: make printk more robust by not allowing recursion

since then printk shouldnt deadlock anymore, even if called from within
the scheduler.

Btw., ftrace_printk() can be used similarly (and you can capture it
nonstop via /debug/tracing/trace_pipe), and should not deadlock either.

Ingo