KDE processes writing to icon-cache files "prevents the disk from going to powersave mode."

[Dennis Schridde]

Binary package hint: kdebase-workspace

Following are several lines of output from powertop, while doing effectively nothing (despite staring at the output of powertop) with my computer:

The program 'flush-8:0' is writing to file 'kde-icon-cache.index' on /dev/sda1.
This prevents the disk from going to powersave mode.

The program 'plasma-desktop' is writing to file 'kde-icon-cache.lock.lN2736' on /dev/sda1.
This prevents the disk from going to powersave mode.

The program 'plasma-desktop' is writing to file 'kde-icon-cache.lock.QP2736' on /dev/sda1.
This prevents the disk from going to powersave mode.

Running powertop for a longer time will result in lots of such messages. To me it seems not immediately necessary to frequently write to such cache files, and create lock files, if the icon theme does (almost) never change.

Kubuntu 10.04_beta1 / Lucid
kdebase-workspace 4:4.4.1-0ubuntu6

[Dennis Schridde (devurandom)]

The program 'konqueror' is writing to file 'kde-icon-cache.lock.Th3204' on /dev/sda1.
This prevents the disk from going to powersave mode.

(while sending this bugreport)

[Jonathan Thomas (echidnaman)]

Hi there!

Thanks for reporting this bug! Your bug seems to be a problem with the KDE program itself, and not with our KDE packages. While we appreciate your issue, it would be better if it was tracked at https://bugs.kde.org, so that the KDE developers can deal with this speedily and have direct communication with you as the reporter for more effective debugging.

Thanks!

[Dennis Schridde (devurandom)]

Version: (using KDE 4.4.1)
Installed from: Ubuntu Packages

Following are several lines of output from powertop, while doing effectively nothing (despite staring at the output of powertop or writing this bugreport) with my computer:

The program 'flush-8:0' is writing to file 'kde-icon-cache.index' on /dev/sda1.
 This prevents the disk from going to powersave mode.

The program 'plasma-desktop' is writing to file 'kde-icon-cache.lock.lN2736' on /dev/sda1.
 This prevents the disk from going to powersave mode.

The program 'plasma-desktop' is writing to file 'kde-icon-cache.lock.QP2736' on /dev/sda1.
 This prevents the disk from going to powersave mode.

The program 'konqueror' is writing to file 'kde-icon-cache.lock.Th3204' on /dev/sda1.
 This prevents the disk from going to powersave mode.

Running powertop for a longer time will result in lots of such messages. To me it seems not immediately necessary to frequently write to such cache files, and create lock files, if the icon theme does (almost) never change.

Kubuntu 10.04_beta1 / Lucid
 kdebase-workspace 4:4.4.1-0ubuntu6

[Dennis Schridde (devurandom)]

The program 'plasma-desktop' is writing to file 'plasma_theme_air-netbook.index' on /dev/sda1.
This prevents the disk from going to powersave mode.

[Dennis Schridde (devurandom)]

Possibly related:

[/usr/bin/akonadi_maildir_resource] akonadi_maildir_resource_0(5724): Failed to lock file "/var/tmp/kdecache-$USER/kpc/kde-icon-cache.lock" , last result = 1

[/usr/bin/akonadi_nepomuk_contact_feeder] akonadi_nepomuk_contact_feeder(5727): Failed to lock file "/var/tmp/kdecache-$USER/kpc/kde-icon-cache.lock" , last result = 1

[Mpyne (mpyne)]

Simply grabbing an icon from the cache, even if it's already cached and didn't need to be grabbed from disk, will result in updating the index file for the cache to update the usage count and last access time (similar to the behavior of filesystems without the noatime mount option)

It's possible to just add a flag to stop that I suppose, but probably easier at this point to not load icons unnecessarily when idle (although I don't know that is actually what's going on!)

[Stefan Bruens (stefan-bruens)]

(In reply to comment #3)
> It's possible to just add a flag to stop that I suppose, but probably easier at
> this point to not load icons unnecessarily when idle (although I don't know
> that is actually what's going on!)

There is a bug in qpixmapcache (or qpc is used with a different scope). qpc evicts entries from the cache after some time, even if the items are in use, when the set of items is stable (e.g., you only use the same 3 pixmaps all the time). I am currently working on a new implementation for qpc which does not show this behaviour.

[Vladimir Prus (vladimir-prus)]

Is there any progress on this? KDE 4.5.1 as shipped by Kubuntu still has this annoying behaviour.

[Mpyne (mpyne)]

No one has submitted any patches. The implementation of the icon cache has shifted over to KSharedDataCache in the meantime. Perhaps the best route is to add an internal (i.e. not part of the public API) option to KSharedDataCache::find() to not update the use count on access (similar to noatime in mount) and then have KSharedDataCache::Private not update use counts if PowerDevil says we're on "powersave".

[Gerlando Lo Savio (gerlos)]

I'm experiencing the same behaviour on my KDE 4.5.1 system running on Kubuntu 10.04.

[Nate-b (nate-b)]

Is this still a problem in recent versions of Plasma 5, like 5.19 or later?

[Dennis Schridde (devurandom)]

(In reply to Nate Graham from comment #8)
> Is this still a problem in recent versions of Plasma 5, like 5.19 or later?

I doubt it.

[Dennis Schridde (devurandom)]

(In reply to Dennis Schridde from comment #9)
> (In reply to Nate Graham from comment #8)
> > Is this still a problem in recent versions of Plasma 5, like 5.19 or later?
>
> I doubt it.

I just tried to check this, but powertop 2.13 no longer provides this kind of information.

I also found a machine that still has a spinning hard drive. I can hear that the drive goes into standby and is woken up again immediately thereafter. Without a tool to analyse which program is responsible, I do not think we stand a chance to improve this.