slow batch conversion

Gilles Caulier caulier.gilles at
Sun Aug 20 10:03:39 BST 2017


There are few explanation to give here about multi threading.

In digiKam all is multi-threaded when this can be and when it's give
improvements of speed :

- mostly all image editor tools use multi-core.
- mostly all BQM tools use multi-core (same code than editor in fact).
- BQM queue can be multi-threaded (more than one at the same time).
One core or multi-core (optional)
- Maintenance tools : same as BQM queue.
- The database access is now ported to multi-cores/multi-threads (KIO
slaves was used before). It use always all core to process, but some
bottleneck can appear with database if too much query are queue in
interface, especially with sqlite. Mysql is better in this case.
- Face management use multi-core or not.
- Assistants as panorama, emailimages, pseudoHDR, HTMLGallery,
Videoslideshow : all are mutithreaded, and some tools use multi-core,
some not, as videoslideshow which serialize a video flux from images
(encoding with ffmpeg use multicore).

What do not use multicore :

- Scan items : even if it run in a separated thread, it do not use
multicores yet.
- Download items from camera : there is a bottleneck with concurrent
media access. It use a separate thread at least.

Note there is a bug about multi-core support fixed in next 5.7.0 which
can introduce huge time latency in previous versions. This fix is a
big step in stabilization of application.


Gilles Caulier

2017-08-20 0:03 GMT+02:00 fotografie <fotografie at>:
> Hello,,
> I had the same problem with digikan 5.4.
> The batch converison worked really slow. But I found an entry in the
> menu to tell digikam to use all prozessor kernels. And that speeded it
> up. Now I have the problem again with digikam 5.6 and 5.7. Where can I
> set digkam up to use all cpus?
> Thanks in advance for your help.
> Best regards Ulf

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