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

Ingo Molnar
2007-11-15T19:35:35Z

* Mark Lord <lkml@rtr.ca> wrote:

>> Can you try nohz=off highres=off? Strange stuff is happening with
>> nohz.
>
> (added Ingo to CC: list: maybe this is some weird interaction with CFS
> and jiffies being reset to 0 on resume ??)

hm, CFS should have no impact here. To see what's happening you could
try to use the latency tracer of the -rt patch and do a cross-resume
trace.

pick up the latest latency tracer patch from:

http://redhat.com/~mingo/private/latency-tracer-v2.6.24-rc2-git5-combo.patch

apply it and enable CONFIG_FUNCTION_TRACING, then pick up trace-cmd.c:

http://redhat.com/~mingo/private/trace-cmd.c

and do something like:

./trace-cmd pm-suspend > trace.txt

or:

./trace-cmd /bin/bash -c "echo ram > /sys/power/state" > trace.txt

this should trigger suspend - then you should do the resume. If
everything goes well then trace.txt should contain a pretty large trace
of all the stuff we do during a suspend+resume.

and wait for such a pause and send us the resulting trace.txt.

if it's an SMP box then first do:

echo 1 > /proc/sys/kernel/trace_all_cpus

to get a global trace. Let me know if something doesnt work with this
scheme.

Ingo