Bug 375035

Summary: Out of memory during face tagging
Product: [Applications] digikam Reporter: lesf
Component: Faces-DetectionAssignee: Digikam Developers <digikam-bugs-null>
Severity: crash CC: caulier.gilles, mario.frank, metzpinguin
Priority: NOR    
Version: 5.6.0   
Target Milestone: ---   
Platform: Arch Linux   
OS: Linux   
Latest Commit: Version Fixed In: 5.8.0

Description lesf 2017-01-14 10:54:16 UTC
digikam crashes (killed by kernel) during tagging of detected faces due to out-of-memory.

Last entries (lots of them) of digikam in the system journal:
   digikam.facesengine: Clone Array size [ 1 ,  16384 ] of type  5

recognition.db is about 214MB
around 29700 tagged faces

It used to be better in 5.3 (admittedly the number of tagged faces were smaller, say ~27000)
Comment 1 caulier.gilles 2017-01-14 10:57:26 UTC
Please try the Linux Universal AppImage bundle instead system based package.
There is nothing to install. Run it as well.


Face tagging use OpenCV in background. I suspect that system based OpenCV is badly packaged (a puzzle). The AppImage include OpenCV with the minimum component enabled.

Gilles Caulier
Comment 2 lesf 2017-01-14 12:59:28 UTC
Tried the AppImage, unfortunately the same effect.

It seems OK if only a few (3, 4) persons are tagged. As soon as there were too many (different) persons tagged in the current session, the system runs out of memory.

I checked the system log, it contains a lot of following entries (with slightly different numbers):
digikam.facedb: Checkout compressed histogram  10039  for identity  4  with size  9377
Comment 3 lesf 2017-01-14 14:33:41 UTC
Downgraded to 5.3, to no avail.

I had a closer look into the system log: it seems that for every new face, Digikam runs this "digikam.facedb: Checkout compressed histogram".

Say, I'm currently tagging 'Alice'. I see the 'Checkout compressed histogram' only for the first time I tag 'Alice'. Tagging following 'Alice' faces don't trigger a checkout. Now, when I want to tag 'Bob', the 'Checkout compressed histogram' runs again, eats up all my memory, and Digikam gets killed.

So, work-around for me: tag all faces of one person, restart Digikam, tag another person, and so on. Not a very nice workflow :-/
Comment 4 Maik Qualmann 2017-01-14 19:30:27 UTC
Is your recognition.db still created with digiKam-4.xx? Please rename the recognition.db and try again. Actually this problem was fixed in the last versions of digiKam-4.xx. But it was necessary to create a new DB.

Comment 5 lesf 2017-01-14 19:57:47 UTC
Yes, the recognition.db was created newly by Digikam 5.x (next to digikam4.db and the thumbnails)
Comment 6 lesf 2017-01-17 20:21:50 UTC
After activating swap digikam doesn't crash anymore -- it eats up most of the RAM, though.
I guess it doesn't allocate any more memory because OpenCV is miffed and throws exceptions for every face-tagged picture:
    digikam.facesengine: Default exception from OpenCV
Comment 7 Mario Frank 2017-02-28 16:04:58 UTC
(In reply to lesf from comment #6)
> After activating swap digikam doesn't crash anymore -- it eats up most of
> the RAM, though.
> I guess it doesn't allocate any more memory because OpenCV is miffed and
> throws exceptions for every face-tagged picture:
>     digikam.facesengine: Default exception from OpenCV

Can you test with the current AppImage again? I have done some changes in 5.5.0 which reduce the count of created threads. This may also have lead to out of memory problems. It is possible that your problem does not occur any more.

The most current AppImages are always stored here by Gilles:
Comment 8 lesf 2017-02-28 18:52:44 UTC
Unfortunately, this appimage doesn't work either.
Still the same effect as I wrote in comment #2: tagging a few persons is OK, but after that, the system runs out of memory.
Comment 9 caulier.gilles 2017-02-28 19:04:58 UTC
Do you use Sqlite or Mysql as database ?

Can you reproduce the problem using a fresh account and a fresh database (data can be corrupted with previous crashes) ?

Gilles Caulier
Comment 10 lesf 2017-03-02 19:15:59 UTC
I use Sqlite database.

I can reproduce the problem.
- Created a new user account
- Prepared a data set of ~58000 pictures. Stripped all metadata [exiftool -r -overwrite_original -P -all= DIR], as they contained face tags and regions
- Started digikam (digikam-5.5.0-01-x86-64.appimage from 27.2.2017, Revision 7e3182fb6562c8bc01d689dcce9b99c7215b2ae9)
- Run face detection with vanilla settings -- around 28000 faces were detected
- In the 'unknown' tag, I selected groups of images (ignoring whether they were actual faces or faces from different persons) and assigned them to different 'persons'. Current status:
  'Person A' ~ 10.000 tags
  'Person B' ~ 10.000 tags
  'Person C' ~ 4.500 tags
  7 other persons with 20 to 400 tags
- Now, selecting more images and assigning them to a person resulted in a forced kill by the kernel due to memory exhaustion.

recognition.db is ~219MB

The system has 8GB RAM, and no swap. My normal working set of usually running programs is ~1 GB RAM.
Comment 11 caulier.gilles 2017-04-16 20:21:58 UTC
new 5.6.0 pre-release as bundle is available here :


Please check if this problem still reproducible with these versions.

Thanks in advance

Gilles Caulier
Comment 12 lesf 2017-04-22 18:26:05 UTC
Issue still exists for 5.6.0 pre-release

- 62800 pictures, JPG only
- stripped metadata, re-compressed with ImageMagick to save disc space and exclude JPG issues (mogrify -strip -quality 50)

Start digikam:
  cd /var/tmp/dkdebug
  ./digikam-5.6.0-01-x86-64.appimage --config /var/tmp/dkdebug/digikam-5.6.0.config

Vanilla digikam setup

Started face detection with default settings
2 x crashes (if the "Unknown" tag is selected while the detection is running)
~ 28900 faces (+ other) detected
Created 3 persons
Assigned ~10'000 faces to Person A, ~10'000 faces to Person B, ~5'000 faces to Person C by selecting the thumbnails and assigning a name

Now, if a picture is opened and there are unassigned face tags in it, digikam crashes with out-of-memory if I set a name to an unassigned face

digikam4.db: 28M
recognition.db: 213M
thumbnails-digikam.db: 1,7G
Comment 13 Maik Qualmann 2017-12-17 19:21:34 UTC
Git commit 6a9fd9891a3ff341dc42fe36158cbf0101d513b6 by Maik Qualmann.
Committed on 17/12/2017 at 19:20.
Pushed by mqualmann into branch 'master'.

delete threads from memory when they are finished
Related: bug 375317, bug 321784, bug 325712, bug 328732, bug 330227, bug 331912, bug 344661, bug 345395, bug 350549, bug 381877, bug 338249, bug 329651, bug 329091, bug 387821, bug 381222

M  +2    -1    NEWS
M  +25   -0    libs/database/dbjobs/dbjobsmanager.cpp
M  +35   -0    libs/iojobs/iojobsmanager.cpp

Comment 14 caulier.gilles 2017-12-17 20:02:16 UTC
Following this commit:


... the approach to fix this problem is under way and new digiKam 5.8.0 pre-release bundles will be compiled tonight to lets a chance to end-users to give a feedback about this fix before the 5.8.0 official release planed before Christmas 2017.

The bundles will be available in 2 hours at this url:


Please do not waste time to test if this file is always valid for next 5.8.0.

Thanks in advance

Gilles Caulier
Comment 15 lesf 2017-12-29 08:32:27 UTC
For digikam-5.8.0-20171227T061903-x86-64.appimage, I couldn't reproduce the issue with my test data set.

=> change status to resolved/fixed