As always, I’m late to the party. But I’m still glad someone has come along and done a comprehensive benchmark of Gentoo’s optimizations, including
-O3 flags for gcc. And it’s probably good to throw Ubuntu into that test too, for another level of comparison.
There were very few surprises there for me — a lot of what the author reports and concludes is similar to my own experiences. For my older systems I usually build Crux with the
-O2 flag, although while I was using machines with a mere 16Mb of memory, I relied on
-Os, and I still try that from time to time. My logic is, if
-Os builds smaller binaries, they should load faster. But maybe I’m overthinking it.
Where you sit on the issue depends a lot on what you use your computer for, and how much performance you require and at what cost. Like so many things with Linux, you have the freedom to sculpt your computer to your liking — or not at all. If you’ve never built a system from source code, it’s worth trying once or twice. If it appeals to you, you won’t mind the time spent doing it. On the other hand, if it doesn’t, you can rely on binary distributions, and there’s no shame in that.
As a final note it’s worth pursuing if you’re working with underpowered or out-of-date hardware. Speaking from experience, a customized system might be what determines whether or not the machine is usable at all.