RE: [Regression] Commit "nvme/pci: Use host managed power state for suspend" has problems

[Mario.Limonciello]

> -----Original Message-----
> From: Rafael J. Wysocki <rafael@xxxxxxxxxx>
> Sent: Thursday, July 25, 2019 12:04 PM
> To: Limonciello, Mario
> Cc: Kai-Heng Feng; Rafael J. Wysocki; Keith Busch; Christoph Hellwig; Sagi
> Grimberg; linux-nvme; Linux PM; Linux Kernel Mailing List; Rajat Jain
> Subject: Re: [Regression] Commit "nvme/pci: Use host managed power state for
> suspend" has problems
> 
> 
> [EXTERNAL EMAIL]
> 
> On Thu, Jul 25, 2019 at 6:24 PM <Mario.Limonciello@xxxxxxxx> wrote:
> >
> > +Rajat
> >
> > > -----Original Message-----
> > > From: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
> > > Sent: Thursday, July 25, 2019 9:03 AM
> > > To: Rafael J. Wysocki
> > > Cc: Keith Busch; Christoph Hellwig; Sagi Grimberg; linux-
> > > nvme@xxxxxxxxxxxxxxxxxxx; Limonciello, Mario; Linux PM; LKML
> > > Subject: Re: [Regression] Commit "nvme/pci: Use host managed power state
> for
> > > suspend" has problems
> > >
> > >
> > > [EXTERNAL EMAIL]
> > >
> > > Hi Rafael,
> > >
> > > at 17:51, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote:
> > >
> > > > Hi Keith,
> > > >
> > > > Unfortunately,
> > > >
> > > > commit d916b1be94b6dc8d293abed2451f3062f6af7551
> > > > Author: Keith Busch <keith.busch@xxxxxxxxx>
> > > > Date:   Thu May 23 09:27:35 2019 -0600
> > > >
> > > >     nvme-pci: use host managed power state for suspend
> > > >
> > > > doesn't universally improve things.  In fact, in some cases it makes
> > > > things worse.
> > > >
> > > > For example, on the Dell XPS13 9380 I have here it prevents the processor
> > > > package
> > > > from reaching idle states deeper than PC2 in suspend-to-idle (which, of
> > > > course, also
> > > > prevents the SoC from reaching any kind of S0ix).
> > > >
> > > > That can be readily explained too.  Namely, with the commit above the
> > > > NVMe device
> > > > stays in D0 over suspend/resume, so the root port it is connected to also
> > > > has to stay in
> > > > D0 and that "blocks" package C-states deeper than PC2.
> > > >
> > > > In order for the root port to be able to go to D3, the device connected
> > > > to it also needs
> > > > to go into D3, so it looks like (at least on this particular machine, but
> > > > maybe in
> > > > general), both D3 and the NVMe-specific PM are needed.
> >
> > Well this is really unfortunate to hear.  I recall that with some disks we were
> > seeing problems where NVME specific PM wasn't working when the disk was in
> D3.
> >
> > On your specific disk, it would be good to know if just removing the
> pci_save_state(pdev)
> > call helps.
> 
> Yes, it does help.
> 
> > If so, :
> > * that might be a better option to add as a parameter.
> > * maybe we should double check all the disks one more time with that tweak.
> 
> At this point it seems so.

OK, I've asked someone in my lab to check across a variety of otherwise working SSDs
with that modification.

Hopefully KH can also accomplish in his lab that as he has more SSDs readily available.

> 
> > > > I'm not sure what to do here, because evidently there are systems where
> > > > that commit
> > > > helps.  I was thinking about adding a module option allowing the user to
> > > > override the
> > > > default behavior which in turn should be compatible with 5.2 and earlier
> > > > kernels.
> > >
> > > I just briefly tested s2i on XPS 9370, and the power meter shows a 0.8~0.9W
> > > power consumption so at least I donât see the issue on XPS 9370.
> > >
> >
> > To me that confirms NVME is down, but it still seems higher than I would have
> > expected.  We should be more typically in the order of ~0.3W I think.
> 
> It may go to PC10, but not reach S0ix.
> 
> Anyway, I run the s2idle tests under turbostat which then tells me
> what has happened more precisely.

To echo the request earlier, it would be good to know exactly which SSD you have
here in your 9380.  Specifically I'd like to know the vendor/model and if the SSD
you're using requests HMB.