Date:	Sun, 26 Sep 2010 00:10:54 +0200
From:	Martin Steigerwald <Martin@...htvoll.de>
To:	Nigel Cunningham <nigel@...onice.net>
Cc:	linux-pm@...ts.linux-foundation.org,
	LKML <linux-kernel@...r.kernel.org>,
	"TuxOnIce-devel" <tuxonice-devel@...onice.net>
Subject: Re: [TuxOnIce-devel] [linux-pm] [PATCH] Hibernate: 
 Implement	readahead when resuming

Hi Nigel.

Am Samstag 25 September 2010 schrieb Nigel Cunningham:
> On 26/09/10 05:58, Martin Steigerwald wrote:
> > Am Samstag 25 September 2010 schrieb Martin Steigerwald:
> >> Hi Nigel and Rafael,
> >> 
> >> Am Samstag 25 September 2010 schrieb Nigel Cunningham:
> >>> Add support for submitting reads before they're needed. This
> >>> greatly improves the speed of resuming:
> >>> 
> >>> From
> >>> 
> >>> PM: Image read at 66 MB/s.
> >>> 
> >>> to
> >>> 
> >>> PM: Image read at 229 MB/s.
> >>> 
> >>> ...and removes the need for the sync_read flag.
> >> 
> >> So
> >> 
> >> martin@...mbhala:~/Computer/Shambhala/Kernel/2.6.36/tuxonice-head> 
> >> git branch -av | grep for-rafael
> >> * for-rafael                      d4e7490 Hibernate: Implement
> >> readahead when resuming
> >> 
> >>    remotes/origin/for-rafael       d4e7490 Hibernate: Implement
> >> 
> >> readahead when resuming
> > 
> > [...]
> > 
> >> basically seems to work.
> > 
> > [...]
> > 
> >> I tried 5 times:
> >> 
> >> - one with just kdm started worked nicely and really rather fast!
> >> 
> >> - four with a full blown KDE 4.5.1 session with OpenGL compositing
> >> 
> >>    - one seemed to hang prior to reinitializing the Radeon KMS DRM
> >>    setup - three other worked just fine
> >> 
> >> I do not think that the hang is related to your changes, Nigel. The
> >> kernel remained stuck at the lower initial resolution and didn't
> >> seem to initialize the radeon KMS framebuffers at 1400x1050
> >> properly. I didn't see this with 2.6.35 and userspace software
> >> suspend.
> > 
> > I am not so sure anymore.
> > 
> > I got another one of these hangs with the 2.6.36-rc5 mentioned above.
> > See IMG_3871.jpg for the exact display were it hung. I was able to
> > switch view with Alt-F1 or something like that. And then got
> > IMG_3873.jpg. But nothing happened anymore. Find these on:
> > 
> > http://martin-steigerwald.de/tmp/tuxonice/hang-after-resume-with-pm-
> > patches-for-rafael/
> > 
> > I now tried in kernel suspend to disk with
> > 
> > martin@...mbhala:~>  cat /proc/version
> > Linux version 2.6.35.5-tp42-vmembase-0-pm-avoid-oom-dirty
> > (martin@...mbhala) (gcc version 4.4.5 20100728 (prerelease) (Debian
> > 4.4.4-8) ) #4 PREEMPT Sat Sep 25 13:29:53 CEST 2010
> > 
> > which doesn't contain your patches, Nigel, for about 5 or 6 times and
> > I did not see that hang.
> > 
> > So maybe something in your patches, even if just the debug output I
> > mentioned, or something in 2.6.36-rc5 triggers that hang.
> > 
> > I will test 2.6.35.5 for a bit longer to make sure that there is no
> > hang on resume prior to loading. I need to reboot this one now too,
> > cause after one of the resume attempts USB stopped working with:
> > 
> > Sep 25 21:36:47 shambhala kernel: usb 1-3: New USB device found,
> > idVendor=1307, idProduct=0330
> > Sep 25 21:36:47 shambhala kernel: usb 1-3: New USB device strings:
> > Mfr=1, Product=2, SerialNumber=3
> > Sep 25 21:36:47 shambhala kernel: usb 1-3: Product: Mass Storage
> > Device Sep 25 21:36:47 shambhala kernel: usb 1-3: Manufacturer:
> > Generic Sep 25 21:36:47 shambhala kernel: usb 1-3: SerialNumber:
> > 00000000000006 Sep 25 21:36:47 shambhala kernel: scsi3 : usb-storage
> > 1-3:1.0 Sep 25 21:36:48 shambhala kernel: BUG: unable to handle
> > kernel NULL pointer dereference at 0000002c
> > Sep 25 21:36:48 shambhala kernel: IP: [<c125b5de>]
> > cfq_get_queue+0x33e/0x550
> > Sep 25 21:36:48 shambhala kernel: *pde = 00000000
> > Sep 25 21:36:48 shambhala kernel: Oops: 0000 [#1] PREEMPT
[...]
> > exited with preempt_count 1
> > 
> > Maybe the USB system has an powermanagement related issue that in
> > kernel suspend triggers more easily than userspace software suspend?
> > I didn't see this one before. But well, this is a bug I will report
> > in
> > bugzilla.kernel.org.
> > 
> > Ciao,
> 
> Okay. Can you try without the last patch, and confirm that it's
> reliable (albeit slower) then?

Well as I told already (later on) the USB problem seems to be related to 
my testing of systemd in Debian - I do not get how this could be the case, 
but it works, when I remove init=/bin/systemd. I think I will report this 
as a kernel bug nonetheless, cause when I apply that "userspace shouldn't 
be able to let the kernel oops" paradigm then its a kernel bug.

Should I test without the readahead patch regarding whether that hang 
after resume, prior to activating Radeon KMS framebuffer is fixed as well?

I am a bit unsure on what to test next. My current thoughts are:

- Test whether 2.6.35.5 is stable with unpatched in kernel suspend. 
Currently in progress. Cause before that I only know its stable with 
userspace software suspend.

- Apply your patches on top of 2.6.35.5 and test that.
  - If that works, it appears to be a problem introduced by 2.6.36-rc5
    - Then I'd possibly test 2.6.36-rc5 with unpatched in kernel suspend.
  - If that doesn't work, it appears to be an issue with your patches
    - Then I test without readahead patch.

Tell me when you have any different suggestions.

Ciao,
-- 
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
GPG: 03B0 0D6C 0040 0710 4AFA  B82F 991B EAAC A599 84C7

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