On 07.02.22 23:45, Bjorn Helgaas wrote: > [+cc linux-kernel for visibility] > > On Wed, Jan 26, 2022 at 06:12:50AM -0600, Bjorn Helgaas wrote: >> On Wed, Jan 26, 2022 at 08:18:12AM +0000, bugzilla-daemon@xxxxxxxxxxxxxxxxxxx wrote: >>> https://bugzilla.kernel.org/show_bug.cgi?id=215533 >>> >>> --- Comment #1 from joey.corleone@xxxxxxx --- >>> I accidentally sent the report prematurely. So here come my findings: >>> >>> Since 5.16 >>> (1) my system becomes unresponsive every couple of seconds (micro lags), which >>> makes it more or less unusable. >>> (2) wrong(?) CPU frequencies are reported. >>> >>> - 5.15 works fine. >>> - Starting from some commit in 5.17, it seems (1) is fixed (unsure), but >>> definitely not (2). >>> >>> I have bisected the kernel between 5.15 and 5.16, and found that the offending >>> commit is 0e8ae5a6ff5952253cd7cc0260df838ab4c21009 ("PCI/portdrv: Do not setup >>> up IRQs if there are no users"). Bisection log attached. >>> >>> Reverting this commit on linux-git[1] fixes both (1) and (2). >>> >>> Important notes: >>> - This regression was reported on a DELL XPS 9550 laptop by two users [2], so >>> it might be related strictly to that model. >>> - According to user mallocman, the issue can also be fixed by reverting the >>> BIOS version of the laptop to v1.12. >>> - The issue ONLY occurs when AC is plugged in (and stays there even when I >>> unplug it). >>> - When booting on battery power, there is no issue at all. >>> >>> You can easily observe the regression via: >>> >>> watch cat /sys/devices/system/cpu/cpu[0-9]*/cpufreq/scaling_cur_fre >>> >>> As soon as I plug in AC, all frequencies go up to values around 3248338 and >>> stay there even if I unplug AC. This does not happen at all when booted on >>> battery power. >>> >>> Also note: >>> - the laptop's fans are not really affected by the high frequencies. >>> - setting the governor to "powersave" has no effect on the frequencies (as >>> compared to when on battery power). >>> - lowering the maximum frequency manually works, but does not fix (1). >>> >>> [1] https://aur.archlinux.org/pkgbase/linux-git/ (pulled commits up to >>> 0280e3c58f92b2fe0e8fbbdf8d386449168de4a8). >>> [2] https://bbs.archlinux.org/viewtopic.php?id=273330 > > I hope we can find a better solution, but since the responsiveness > issue is a significant regression, I queued up a revert of > 0e8ae5a6ff59 ("PCI/portdrv: Do not setup up IRQs if there are no > users") in case we don't find one. Likely best for now. > > If/when we get to the bottom of this, I'll replace the revert with the > solution. 0e8ae5a6ff59 appeared in v5.16, so we'll have to make sure > we fix that as well. If you could give some feedback/hints on the questions I posted last week on the original patch, that might accelerate understanding the real issue. Thanks, Jan -- Siemens AG, Technology Competence Center Embedded Linux
