[ltt-dev] trace_clock_update() spinning

Mike McTernan mmcternan at airvana.com
Tue Feb 2 16:12:38 EST 2010


> Mathieu Desnoyers wrote:
>
> So it's not that LTTng itself is taking time, but that the trace clock
> resolution available for your architecture is really coarse. 

Excellent!  I understand what that means now.  Everything in the trace
is crushed up using the bottom 13-bits of the counter advanced with each
marker, then at the instance the upper bits are updated on the timer
tick the output appears to jump along making it _look_ like the update
function took all the remaining time.  What a fool I was!

> You could possibly get a better resolution by creating a trace clock
> specific for your architecture.

I'm pretty sure there's a general purpose timer hanging around somewhere
on this board if I can't find some sort of performance counter register
with which to improve things.

Many Thanks,

Mike




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