My main question is: does wgMaxShellMemory limit the total memory used by all processes for shell tasks, like ImageMagick thumbnail creation? Or is it rather a per-process limit? The documentation for this setting seems vague.
I have a wiki which is using too much memory on a shared host. I've narrowed the culprit down to ImageMagick using too much memory when converting uploaded images. I've reduced the max upload size in php.ini, which will help, but I was hoping wgMaxShellMemory would serve as a hard limit for total memory usage by ImageMagick and other MediaWiki background processes.
As a sidenote, I also couldn't figure out from documentation whether image conversion is a part of the job queue, thus allowing wgJobRunRate to slow down thumbnail creation.