Comment # 20 on bug 1131437 from Giovanni Gherdovich

Created attachment 804345 [details]
second page extract from the full report

Another page to show that the patterns described previously hold in general.
Next I'm going to attach a 3rd page.

The full report in the form of a multi-page PDF file is at
https://w3.suse.de/~ggherdovich/BSC1131437/flipbook-dbench-2clients.pdf
(~50 MB)

Code and data for the plot is at
https://gitlab.suse.de/ggherdovich/dbench-migrations

Things I forgot to mention in the previous comment:

* a shortcoming of this plots is that the xfs kworker journaling thread is not
traced. I haven't thought yet at how to grab it; probably I could insert a
static tracepoint in the XFS entry point and recognize the interesting kworker
that way. After that is done, crossing data with pstate migration is the same
as already done

* tracing was done with systemtap being careful not to do any IO while the
benchmark was running (all the arrays are kept in memory)

* I verified the regression was present when collecting the data, i.e. tracing
didn't interfere with the benchmark results