On 10-11-30 03:30 PM, Mathieu Desnoyers wrote:
* Matthew Khouzam ([email protected]) wrote:
Hello world,
When you have different events in different tracefiles of the same trace
that have the same timestamp, is the order of reading supposed to be
pre-determined?
An example to better illustrate my question.
If at 100ns you have a kernel softIrqEntry and a fs open that occur.
Would you have a prefered order of reading the trace, and could this
affect the state machine.
If two events happen in different trace files at exactly the same time,
there is nothing we can tell about the ordering. So their relative order
is not important, even though it could affect the state machine in rare
cases.
Do you have any examples of such cases?
The way I see it, if we have events from different files with the same
timestamp, they would most probably be unrelated. If we do get
"conflicting" information (a file open and a file close on the same
file, by the same process, at the same time), this would probably be a
problem with the kernel or more likely the tracing mechanism.
Alexandre
Ideally, the state machine should become clever enough to detect
these cases where relative ordering of events is unknown based on
timestamps delta being under a certain threshold, or based on other
instrumentat (interrupt execution surrounding the event). I'm not saying
that LTTV and TMF are doing a particularly good at this at the moment --
it should be considered as something to improve.
Thanks,
Mathieu
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