dtrace discuss - Nov 2007 - sysinfo:::pswitch fires ''before'' or ''after'' the context switch?

Can anyone confirm if sysinfo:::pswitch/sysinfo::preempt:inv_swtch fires
''before'' or ''after'' the context switch?

I know sched:::off-cpu fires before the context switch, but not quite sure about
sysinfo:::pswitch and sysinfo::preempt:inv_swtch.If these fire after the context
switch, is there any way to use sched:::off-cpu and still be able to distinguish
between voluntary and involuntary context switches?

Thanks,
Neelam


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Neelam wrote:
> Can anyone confirm if sysinfo:::pswitch/sysinfo::preempt:inv_swtch fires
''before'' or ''after'' the context switch?
   They fire before the context switch.

   sysinfo::preempt:inv_swtch fires before calling swtch().
 
http://cvs.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/uts/common/disp/disp.c
  [look for the definition of preempt in the above file]

   The probe sysinfo:::pswitch is placed before the call to resume() in
   swtch() and hence would fire before the sched:::off-cpu probe in
   resume().
   [look for the definition of swtch() in the above url]


Pramod

> 
> I know sched:::off-cpu fires before the context switch, but not quite sure
about sysinfo:::pswitch and sysinfo::preempt:inv_swtch.If these fire after the
context switch, is there any way to use sched:::off-cpu and still be able to
distinguish between voluntary and involuntary context switches?
> 
> Thanks,
> Neelam
> 
> 
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Okay Thanks.

I have another related question. Does the sysinfo:::pswitch probe fire only for
a voluntary context switch or both voluntary and involuntary context switches?


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Neelam wrote:
> Okay Thanks.
> 
> I have another related question. Does the sysinfo:::pswitch probe fire only
for a voluntary context switch or both voluntary and involuntary context
switches?
> 
> 
   The sysinfo:::pswitch probe fires for both voluntary and involuntary
   context switches.

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