[ltt-dev] sys time

[compudj@krystal.dyndns.org (Mathieu Desnoyers)]

* Pierre-Marc Fournier (pierre-marc.fournier at polymtl.ca) wrote:
> Gian Lorenzo Meocci wrote:
> 
> > I want to know if it is possible to obtain this results using lttng trace.
> 
> It is definitely possible.
> 
> > Actually I made a sum of all differences from a
> > kernel_arch_trap_entry/kernel_arch_trap_exit,
> > kernel_arch_syscall_entry/exit, kernel_softirq_entry/exit,
> > mm_handle_fault_entry/exit, kernel_irq_entry/exit.
> 
> You don't need mm_handle_fault_entry/exit because they are always
> enclosed within kernel_arch_trap_entry/exit's.
> 
> > But for now, my results isn't very good.
> 
> - You need to stop counting time when your process is being scheduled
> out. See the kernel_sched_schedule events.
> 
> - You need to filter the events based on the pid of the process you're
> investigating, but I guess you're already doing that.
> 
> - If the process is being created inside the trace, you need to start
> counting time only after it is created, of course. You could count
> syscall time starting at the kernel_process_fork that creates the
> process. Also, you need to stop counting time when it's destroyed of course.
> 
> - If the process already exists when the trace is started, only consider
> events after the list_statedump_end event. Before that, the pid of each
> event might not be reliable.
> 

All the above is good. Another thing : if an interrupt handler is
executed on top of system call code, don't count it twice. :)

Mathieu

> pmf
> 
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Mathieu Desnoyers
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