[Gimp-user] Debugging Perf on Linux

[Robert Bieber <gimp biebersprojects com>]

This morning I saw the new RC was out, and just to do a quick check on 
performance I downloaded it on my work laptop, loaded a large (~40MP) 
image, and did some quick operations to see how things shook out.  
Everything was pretty smooth, even better than the current stable 
version on my desktop.

Then today I got home, installed the RC on my home desktop, which is a 
significantly beefier machine (32-core thread ripper, 32GB of RAM), 
loaded up a similarly sized image, and found it completely unusable.  It 
hangs simply trying to zoom in and out of the image. Running the wavelet 
decompose takes minutes.  And curiously, even though the window 
frequently stops responding and the process makes my computer fans sound 
like a jet engine, on the new dashboard display the CPU is never ticking 
above 3% and I'm sitting at around 70% of the 12GB of cache I gave it 
used (it was below 50% before I started running the plugin).  This seems 
to be the case regardless of how many threads I enable or whether OpenCL 
is turned on.

I assume this has to be a bug, since I'm running the same software and 
getting the exact opposite of the results I'd expect running it on 
different machines, but what can I do to diagnose it and get some data 
that might help resolve it?  The error console isn't showing anything, 
here's what I get in my terminal when opening an image and running 
wavelet decompose, if that helps at all: https://pastebin.com/TCEgYqPr

Seeing color management stuff in the console did make me think to try 
turning color management off, which did make basic image operations run 
faster, but wavelet decompose is still running intolerably slow.  And of 
course retouching with color management disabled isn't an ideal 
long-term solution.  Any ideas?

Thanks,
Robert