<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body> <div> <a class="bz_bug_link bz_status_NEEDINFO " title="NEEDINFO - rc6_residency_ms unreliable" href="https://bugs.freedesktop.org/show_bug.cgi?id=94852#c6">Comment # 6</a> on <a class="bz_bug_link bz_status_NEEDINFO " title="NEEDINFO - rc6_residency_ms unreliable" href="https://bugs.freedesktop.org/show_bug.cgi?id=94852">bug 94852</a> from <a class="email" href="mailto:lenb@kernel.org" title="Len Brown <lenb@kernel.org>"> Len Brown</a> <pre>turbostat does not poll, it reads the value at the start of a measurement interval, and then reads it again at the end. the measurement interval can be of arbitrary length, (and multiple copies of turbostat could be running at the same time with different measurement intervals) turbostat has a sanity check that the ending value is not smaller than the starting value, but that detects only 1 wrap, and if there have been multiple wraps, it will print erroneous results. turbostat opens and closes the sysfs file for each of these reads. Yes, this problem is much more in-your-face on BYT, which appears to have a wrap at about 13 seconds (Linux-4.10) while /bin/true; do cat /sys/class/drm/card0/power/rc6_residency_ms; sleep 1; done 1394 2408 3423 4436 5451 6463 7474 8488 9503 10516 11529 12542 671 1685 2699 3713 4727 5741 6753 7767 8781 9794 10807 11821 12835 964 1977 2992 4005 5018 6032 7046 8060 9073 10087 11101 12114 243 1255 2268 3283 4295 5309 6323 7334 8349 9363 10374 11386 12401 529</pre> </div> <hr> You are receiving this mail because: <ul> <li>You are on the CC list for the bug.</li> <li>You are the assignee for the bug.</li> <li>You are the QA Contact for the bug.</li> </ul> </body> </html>