Re: [patch] voluntary-preempt-2.6.9-rc2-mm4-S7

[Ingo Molnar]

* Lee Revell <rlrevell@xxxxxxxxxxx> wrote:

> On Mon, 2004-09-27 at 20:05, Ingo Molnar wrote:
> > i've released the -S7 VP patch:
> > 
> >   http://redhat.com/~mingo/voluntary-preempt/voluntary-preempt-2.6.9-rc2-mm4-S7
> 
> Disabling latency tracing does not seem to work.  To demonstrate:
> 
> 	echo 0 > /proc/sys/kernel/preempt_max_latency
> 	echo 0 > /proc/sys/kernel/trace_enabled
> 	modprobe foo-module (will reliably cause a ~3-600 usec latency in resolve_symbol)
> 	check /proc/latency_trace, or dmesg, it will be the modprobe latency.
> 	cat /proc/sys/kernel/trace_enabled, it is still 0
> 
> This definitely worked at one point.  Not sure when it broke.

is it the full modprobe latency trace, or just the header?  Putting zero
into trace_enabled wont disable the critical-section-timing code - it
only disables the function tracer. Since /proc/latency_trace takes the
header portion from the latency-timing code that might change. To
disable both do something like:

  echo 100000000 > /proc/sys/kernel/preempt_max_latency
  echo 0 > /proc/sys/kernel/trace_enabled

	Ingo
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