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Old 2020-10-16, 13:02   #6
M344587487's Avatar
"Composite as Heck"
Oct 2017

3×263 Posts
Default Run from RAM, no NVMe present

Tried running an Ubuntu livecd from RAM (by adding toram as a boot parameter so the USB stick can be removed, entire OS resides in RAM), so that the NVMe could be removed entirely to see how much impact the SSD power draw has. It was a massive failure. Updated OS, power target set to 11W, tlp not installed as it wouldn't on the livecd so the comparison point is in the first table. The no-NVMe timings are just over 8ms/it with the same wall power draw, compared to the 5.55ms/it figure from above it's a massive regression. The 5.55ms/it figure was headless but I tried again with it not headless using both i3 and gnome and the timings stayed the same within variability. A livecd uses a few extra gigs of RAM as storage but they shouldn't be in active use so that shouldn't hinder p95 timings, and I was under the impression that all 32GB of RAM has to be refreshed regardless of whether it's in use so RAM occupancy shouldn't matter when it comes to power draw. To rule occupancy out a ramdisk occupying most of the remaining RAM was created, filled with random data instead of zeroes just incase that matters. As expected there was no noticable difference to timings or power use.

Can't see how removing the NVMe can be a massive negative, at worst there should be no difference and at best a power save, so the conclusion is that a livecd just has some undetermined nonsense that makes it unsuitable for use as a compute environment. Doesn't make a lot of sense as if anything I'd expect a livecd to be lighter on the system than its installed counterpart, but there we are.

Last fiddled with by M344587487 on 2020-10-16 at 13:47 Reason: title
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