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DateMon, 4 Jun 2007 16:17:18 +0200
FromIngo Molnar <>
SubjectRe: [bug] very high non-preempt latency in context_struct_compute_av()

* James Morris <jmorris@namei.org> wrote:

> > the latency is caused by a _very_ long loop in the SELinux code:
> >
> > sshd-4828 0.N.. 465894us : avtab_search_node (context_struct_compute_av)
>
> What do the 0DNs fields mean and what did you use to create this
> trace?

i used the latency tracer from -rt. Here's the meaning of the fields:

_------=> CPU#
/ _-----=> irqs-off
| / _----=> need-resched
|| / _---=> hardirq/softirq
||| / _--=> preempt-depth
|||| /
||||| delay
cmd pid ||||| time | caller
\ / ||||| \ | /
trace-it-4751 0D... 0us : __next_cpu (user_trace_start)
it's very easy to interpret: it traces all the function calls the kernel
executes, and puts the symbolic function name (and its parent function)
into the trace, time ordered. So it's a proper execution trace. Normally
you can ignore the 'DN' type of flags - what matters in this case is the
observed 130 msecs latency and the functions that were called while that
latency happened.

Ingo
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