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

Mike Galbraith
2007-11-16T13:53:34Z

On Fri, 2007-11-16 at 12:23 +0100, Ingo Molnar wrote:
> * Ingo Molnar <mingo@elte.hu> wrote:
>
> > once that tracer bug was fixed, the best method to generate a trace
> > was to do this:
> >
> > echo 1 > /proc/sys/kernel/stackframe_tracing
> > echo 1 > /proc/sys/kernel/syscall_tracing
> > ./trace-cmd bash -c "echo mem > /sys/power/state" > trace.txt
>
> so here's an UP suspend+resume trace i did:
>
> http://redhat.com/~mingo/latency-tracing-patches/misc/trace-suspend-long.txt.bz2
>
> tons of detail - which might be interesting to other folks as well. Fact
> is, our suspend-to-RAM+resume cycle is very, very slow, even on fast
> hardware - and this trace shows all the reasons why.
>
> This was a fully cached system - i.e. i've done a suspend+resume before
> to warm up the caches. (not that suspend+resume does much IO normally.)
>
> The trace shows that a suspend+resume cycle is 7.95 seconds long
> (without counting the time the box spent suspended) - ouch! This was a
> T60 with Core2Duo 1.83GHz.

Ouch? That's an order of magnitude faster than my 3GHz P4 :)

-Mike