| [tracecompass-dev] Synchronizing LTTng Kernel and UST Traces ? |
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Hi Tracecompass Experts, I have obtained an LTTng-UST and Kernel Trace in parallel, but looking at the respective combined experiment it turns out that Kernel and UST seem to use different
time sources (there’s a time skew). Consider attached screenshot: The UST event is shown in the middle of syscall state, but it would be expected in “lemon_server RUNNING” state. Reading the Trace Compass docs, I see that there’s a synchronization feature, but only for network traces and only with experimental branches enabled.
What could be done to get Kernel and UST traces synchronized ? Or should a completely different method of data gathering be considered, eg doing “perf record”
with uprobes enabled and then converting the perf.data to CTF for investigation ? Correlating application traces with Kernel event seems a powerful tool to me for understanding excessive latencies … perhaps adding UST pthread events could help with trace synchronization
since these should exist on Kernel and UST side ? Many thanks for any pointers !! PS my sample trace was obtained on Linux qemux86, Kernel 4.1 with lttng-2.6. I’m happy to share the recorded traces if anybody is interested. Thanks, Martin -- Martin Oberhuber, SMTS / Product Owner – Development Tools,
Wind River direct +43.662.457915.85 fax +43.662.457915.6 |
Attachment:
lttng_merged_kernel_and_ust.png
Description: lttng_merged_kernel_and_ust.png
