hwlat-detector: Update hwlat_detector to add outer loop detection

The hwlat_detector reads two timestamps in a row, then reports any
gap between those calls. The problem is, it misses everything between
the second reading of the time stamp to the first reading of the time stamp
in the next loop. That's were most of the time is spent, which means,
chances are likely that it will miss all hardware latencies. This
defeats the purpose.

By also testing the first time stamp from the previous loop second
time stamp (the outer loop), we are more likely to find a latency.

Setting the threshold to 1, here's what the report now looks like:

1347415723.0232202770	0	2
1347415725.0234202822	0	2
1347415727.0236202875	0	2
1347415729.0238202928	0	2
1347415731.0240202980	0	2
1347415734.0243203061	0	2
1347415736.0245203113	0	2
1347415738.0247203166	2	0
1347415740.0249203219	0	3
1347415742.0251203272	0	3
1347415743.0252203299	0	3
1347415745.0254203351	0	2
1347415747.0256203404	0	2
1347415749.0258203457	0	2
1347415751.0260203510	0	2
1347415754.0263203589	0	2
1347415756.0265203642	0	2
1347415758.0267203695	0	2
1347415760.0269203748	0	2
1347415762.0271203801	0	2
1347415764.0273203853	2	0

There's some hardware latency that takes 2 microseconds to run.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

0 files changed, 0 insertions, 0 deletions