pt-diskstats 2.1 returns garbage

[Maciej Dobrzanski]

I noticed pt-d 2.1 behaves strangely, so I ran iostat, pt-diskstats 2.0 and pt-diskstats 2.1 side by side. Both iostat & pt-d 2.0 returned similar results and my assumption is these were the correct results as well. At the same time pt-d 2.1 showed very different values.

The command lines were:

iostat -x 1 | grep 'sdc '
percona-toolkit-2.0.2/bin/pt-diskstats -c 'rd_s|wr_s' -d 'sdc$'
percona-toolkit-2.1.1/bin/pt-diskstats --columns-regex='rd_s|wr_s' --devices-regex='sdc$'

I attached the graph showing the results I got.

[Maciej Dobrzanski (mushu)]

I forgot to mention that the graph only shows reads/s statistics.

[Baron Schwartz (baron-xaprb)]

Like bug 942773, this is a duplicate of bug 952727. The fix is to use a different --group-by option, and this will become the default in the release that will be available in a couple of days.