Hi,
Why does FromDevice->_task_cycles not include the cycles spend in ToHost
in this config:
FromDevice -> ToHost
When checking cpu-cyclecounts with --enable-stats=2
(x68_64,,somewhat recent click-git on 2.6.24.7 kernel with patches,
opteron 1210 with tsc locked to cpu-clock),
I'm getting these average cycle-counts per packet:
FromDevice:
task 2380
ToHost
self 4800
child 0
No, when looking at the code, this is what I believe should happen:
Task::fire(FromDevice)
task.hh:574 initialize the start_cycles reference
click_cycles_t start_cycles = click_get_cycles();
task.hh:582 Element->run_task is called
FromDevice::run_task
fromdevice.cc:389 output(0).push called
Element::Port::push relevant part verbatim:
click_cycles_t c0 = click_get_cycles();
_e->push(_port, p);
click_cycles_t x = click_get_cycles() - c0;
++_e->_calls;
_e->_self_cycles += x;
ok, now we have recorded the ~4800 ToHost cycles...
then return to task.hh
task.hh:593
_owner->_task_cycles += click_get_cycles() - start_cycles;
this records only the 2380 task cycles.... why?
IMHO: the _task_cycles variable should count all cycles, also the ones
spend in the callee... But it apparently does not.
And the source says
element.hh:
click_cycles_t _task_cycles; // Cycles spent in self from tasks.
That seems to be the case... why only self???
Can somebody please explain the underlying magic to me?
Thanks
Harald
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