On Sun, 2 December 2007 21:07:22 +0100, Ingo Molnar wrote:
quoted text
> * Jörn Engel <joern@logfs.org> wrote:
> 
> > Result looked like a livelock and finally convinced me to abandon the 
> > latency tracer.  Sorry, but it appears to be the right tool for the 
> > wrong job.
> 
> hm, we routinely use it in -rt to capture "what on earth is happening" 
> incidents. The snippet below is a random snipped from a trace that i've 
> just captured, with mcount enabled. It seems to work fine here, with and 
> without mcount. (pit clocksource is almost never used, that's why you 
> had those early problems.)
> 
> oprofile helps if you can reliably reproduce the slowdown in a loop or 
> for a long amount of time, with lots of CPU utilization - and then it's 
> also lower overhead. The tracer can be used to capture rare or complex 
> events, and gives the full flow control and what is happening within the 
> kernel.

Such a trace would be useful indeed.  But so far the patch has only
given me grief and nothing remotely like useful output.  Maybe I should
simply use the complete -rt patch instead of debugging the broken-out
latency-tracer patch.

Jörn

-- 
Mundie uses a textbook tactic of manipulation: start with some
reasonable talk, and lead the audience to an unreasonable conclusion.
-- Bruce Perens
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