Messages in this thread | | | Date | Wed, 23 Apr 2008 11:46:44 +0200 | From | Ingo Molnar <> | Subject | Re: [git pull] scheduler changes for v2.6.26 |
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* Frans Pop <elendil@planet.nl> wrote:
> If I enable tracing with these settings, I get data in both trace > *and* in latency_trace. Is the last correct? From > http://lkml.org/lkml/2008/2/10/43 I got the impression that file > should only be used if the "wakeup" tracer is active.
yeah, that's the intended behavior. 'trace' and 'latency_trace' are two kinds of 'views' on the same set of tracer data (with a different output format). They are both non-destructive - i.e. they dont deplete the trace buffers.
there's even a third view: 'trace_pipe' - which depletes the trace buffers and can be used to pipe trace data into a larger file:
cat trace_pipe > /tmp/large-trace.txt
i guess it would be less confusing if 'trace' and 'latency_trace' was just a single 'view' and its behavior depended on iter_ctl settings. (In fact, we could probably just get rid of latency_trace - it is a leftover from -rt.)
> From the last run I've got three traces with 50000 entries (about a > minute worth each). Traces 1 and 2 should each have two skips and > trace 3 should have four. I've saved both the trace and latency_trace > (ltrace) files. > > They are available at: > http://people.debian.org/~fjp/tmp/kernel/sched/.
thanks, we'll have a look.
> BTW, did either of you actually look at the traces I sent for .24? I > never got any feedback on those.
hm, i looked at them - i thought i mailed you about that but indeed i didnt (sorry about that) - the traces were too short in scope - they just covered a few dozen milliseconds in scope, while your description said that the problem occured seconds into the trace.
> P.S. I've got group scheduling active in this config as my tests with > .24 showed that did not make any difference. Can rerun without if > needed.
no need to rerun - but if you do the next test it might make sense to disable it, just to reduce the number of variables.
another thing - Peter observed skipping on NOHZ. Does your skipping go away if you boot with 'nohz' and/or with CONFIG_NOHZ=y disabled in the .config?
Ingo
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