On 23.05.23 23:49, Bjorn Helgaas wrote: > On Mon, May 22, 2023 at 01:45:55PM +0200, Linux regression tracking (Thorsten Leemhuis) wrote: >> On 05.05.23 08:56, Koba Ko wrote: >>> On Thu, May 4, 2023 at 5:23 PM Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: >>>> [+cc Koba, Ajay, Tasev, Mark, Thomas, regressions list] >>>> On Tue, Apr 11, 2023 at 03:42:29PM -0500, Bjorn Helgaas wrote: >>>>> On Tue, Apr 11, 2023 at 08:32:04AM +0000, bugzilla-daemon@xxxxxxxxxx wrote: >>>>>> https://bugzilla.kernel.org/show_bug.cgi?id=217321 >>>>>> ... >>>>>> Regression: No >>>>>> >>>>>> [Symptom] >>>>>> Intel cpu can't sleep deeper than pcˇ during long idle >>>>>> ~~~ >>>>>> Pkg%pc2 Pkg%pc3 Pkg%pc6 Pkg%pc7 Pkg%pc8 Pkg%pc9 Pk%pc10 >>>>>> 15.08 75.02 0.00 0.00 0.00 0.00 0.00 >>>>>> 15.09 75.02 0.00 0.00 0.00 0.00 0.00 >>>>>> ^CPkg%pc2 Pkg%pc3 Pkg%pc6 Pkg%pc7 Pkg%pc8 Pkg%pc9 Pk%pc10 >>>>>> 15.38 68.97 0.00 0.00 0.00 0.00 0.00 >>>>>> 15.38 68.96 0.00 0.00 0.00 0.00 0.00 >>>>>> ~~~ >>>>>> [How to Reproduce] >>>>>> 1. run turbostat to monitor >>>>>> 2. leave machine idle >>>>>> 3. turbostat show cpu only go into pc2~pc3. >>>>>> >>>>>> [Misc] >>>>>> The culprit are this >>>>>> a7152be79b62) Revert "PCI/ASPM: Save L1 PM Substates Capability for >>>>>> suspend/resume” >>>>>> >>>>>> if revert a7152be79b62, the issue is gone >>>>> >>>>> Relevant commits: >>>>> >>>>> 4ff116d0d5fd ("PCI/ASPM: Save L1 PM Substates Capability for suspend/resume") >>>>> a7152be79b62 ("Revert "PCI/ASPM: Save L1 PM Substates Capability for suspend/resume"") >>>>> >>>>> 4ff116d0d5fd appeared in v6.1-rc1. Prior to 4ff116d0d5fd, ASPM L1 PM >>>>> Substates configuration was not preserved across suspend/resume, so >>>>> the system *worked* after resume, but used more power than expected. >>>>> >>>>> But 4ff116d0d5fd caused resume to fail completely on some systems, so >>>>> a7152be79b62 reverted it. With a7152be79b62 reverted, ASPM L1 PM >>>>> Substates configuration is likely not preserved across suspend/resume. >>>>> a7152be79b62 appeared in v6.2-rc8 and was backported to the v6.1 >>>>> stable series starting with v6.1.12. >>>>> >>>>> KobaKo, you don't mention any suspend/resume in this bug report, but >>>>> neither patch should make any difference unless suspend/resume is >>>>> involved. Does the platform sleep as expected *before* suspend, but >>>>> fail to sleep after resume? >>>>> >>>>> Or maybe some individual device was suspended via runtime power >>>>> management, and that device lost its L1 PM Substates config? I don't >>>>> know if there's a way to disable runtime PM easily. >>>> >>>> Koba, per your bugzilla update, the issue happens even without >>>> suspend/resume. And we don't know whether some particular device is >>>> responsible. >>>> >>>> But if we save/restore L1SS state, we can sleep deeper than PC3. If >>>> we don't preserve L1SS state, we can't. >>>> >>>> We definitely want to preserve the L1SS state, but we can't simply >>>> apply 4ff116d0d5fd ("PCI/ASPM: Save L1 PM Substates Capability for >>>> suspend/resume") again because it caused its own regressions [1,2,3] >>>> >>>> So somebody needs to figure out what was wrong with 4ff116d0d5fd, fix >>>> it, verify that it doesn't cause the issues reported by Tasev, Thomas, >>>> and Mark, and then we can apply it. >>> >>> Good days, discussed with Kai-Heng and he mentioned the GPU may not >>> be pulled off the power. >>> then the GPU needs L1ss to get into power saving. >>> >>> I will investigate further on this way. >> >> Did anything come our of this? >> >> FWIW, I'm considering to drop this from the list of tracked regressions. >> Yes, this is a regression, but it's caused by fix for another (worse) >> regression -- so there is nothing we can do for now anyway (and Koba >> seems motivated already to look properly into all of this). Or does >> anyone consider this to be a problem? > > I would drop this from the regression list. > > Yes, bz 217321 is a bug, and yes, 4ff116d0d5fd is a partial fix for > it, but 4ff116d0d5fd causes worse problems (it breaks resume from > suspend) than just living with bz 217321, which is a "mere" power > consumption issue. Thx for confirming and putting it in better words. #regzbot inconclusive: can't be solved for now, as this is a regression causes by a fix for a regression (see list/bz for details) Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat) -- Everything you wanna know about Linux kernel regression tracking: https://linux-regtracking.leemhuis.info/about/#tldr If I did something stupid, please tell me, as explained on that page.
