[Bug 94852] New: rc6_residency_ms unreliable
bugzilla-daemon at freedesktop.org
bugzilla-daemon at freedesktop.org
Thu Apr 7 03:38:41 UTC 2016
https://bugs.freedesktop.org/show_bug.cgi?id=94852
Bug ID: 94852
Summary: rc6_residency_ms unreliable
Product: DRI
Version: unspecified
Hardware: Other
OS: All
Status: NEW
Severity: normal
Priority: medium
Component: DRM/Intel
Assignee: intel-gfx-bugs at lists.freedesktop.org
Reporter: lenb at kernel.org
QA Contact: intel-gfx-bugs at lists.freedesktop.org
CC: intel-gfx-bugs at lists.freedesktop.org
Kernel: Linux-4.6.0-rc1
Hardware: SKL, HSW
Description:
Value read from /sys/class/drm/card0/power/rc6_residency_ms
resets before it reaches 5500 seconds.
This make it "somewhat awkward" to calculate residence from this counter,
since it can effectively go backwards - or worse, appear to increment
extremely slowly when it should really be incrementing quickly.
turbostat has a workaround for former, but there is no workaround
for the later. powertop does not have a workaround, it will just
occasionally display garbage.
Debug steps taken:
booted both the SKL and HSW with cmdline "i915.enable_dc=0"
but it made no difference.
To Reproduce:
while /bin/true; do cat /sys/class/drm/card0/power/rc6_residency_ms; sleep 1;
done
...
5491367
5492352
5493334
5494326
5495307
5496299
5497280
703
1685
2677
3658
4650
5631
6612
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