Re: [BUG] Strange 1-second pauses during Resume-from-RAM

Ingo Molnar
2007-12-02T15:48:20Z

* Jörn Engel <joern@logfs.org> wrote:

> I do. Went through 10odd runs and annotated the function right below
> mcount each time. Seems to work now.
>
> Trouble is that it doesn't solve my real problem at hand. Something
> is causing significant delays when writing to logfs. Core logfs code
> is not running, but may cause whatever other code is running and
> burning up all the cpu time. Wasting 100ms of "qemu-time" to write a
> single page happens fairly frequently.
>
> With the latency tracer the problem appears to have become worse. Now
> the loftlockup code triggers quite frequently. Which makes a bit of
> sense, as the problem is a busy CPU, rather than an idle one.

well what does the trace say, where do the delays come from? To get a
quick overview you can make tracing lighter weight by doing:

echo 0 > /proc/sys/kernel/mcount_enabled
echo 1 > /proc/sys/kernel/trace_syscalls

(this turns the latency tracer into a "global strace" kind of tracer)

Ingo