Dear experts,

This is an odd question, but it's had me scratching my head. I work on analysis of scientific data using MATLAB based packages, and I often login remotely using nomachine software to run code overnight, so the results are ready for me to inspect in the morning.

I've noticed a few times that when running code overnight, it seems to run extremely slowly. However, when I login in the morning to check progress, it immediately speeds up, simply through my interacting with the MATLAB window to check how it's doing.

It's a big speed change: a processing step that took 17 minutes during the night now takes 2. The speed-up was from the moment I logged on.

No-one else uses the machine, and nothing else, other than the gnome system monitor, is running on the machine. There is an automated night-time backup service, but there's no way that takes all night to run, although I'm wondering if it's somehow re-niceing my analysis code. However, on checking this morning the process has niceness 0, as usual. Also, no swap space is being used, and it's highly unlikely to be a RAM issue, as this analysis uses much less RAM than the machine has.

The machine is a 6-core workstation running SLED SUSE linux.

Any tips on what might be going on much appreciated!

best wishes
George

I would've said the nightly backup was at least partially responsible but you seem to have looked into and ruled this out. Perhaps something changed in your power management settings which is leading to the machine running at lower CPU frequency while it's not "user-busy" overnight to supposedly conserve energy and in which case tweaking these might help.