Comments by "Juzu Juzu" (@juzujuzu4555) on "Configuring a Custom Linux Kernel (5.6.7-gentoo)" video.

3:59 I would assume that with modern CPUs the compression will make the system boot faster if you have HDD and with really fast CPUs it probably is faster even with SSDs. Though NVMe etc. is another story. 8:30 I cannot say for sure, but I think optimizing for size can help with CPUs that have very limited caches. And I would assume it lowers the memory usage, so for ancient computers with minimal RAM this could be the better option. I'm not an expert by any means. Decompression speeds are so huge that mathematically speaking I think the space we save takes more time to load than we add to decompression time on modern CPUs. I have compiled kernel using optimize for size, and I think my Celeron from 2005 was more responsive. But that might have been placebo, as I don't have any solid evidence for it. I had 2gb of RAM with that CPU so there was enough memory. Because that CPU was only 1.6ghz, it had pretty short time per thread until kernel took the control back, and with smaller caches this might have caused much more of loading from RAM with -O2 optimization compared to -Os. Or it might have been just placebo. In any case, it's something worth investigating with old hardware.
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@rockytom5889 You should include the use flag "experimental" for the kernel-sources package, then you have the option "Use GCC autodetected configuration for AMD CPUs" where you normally would select CPU Class. Check out Mental Outlaw on Youtube or Alphanerd on Odysee, he has decent kernel configuration videos that strip down a lot of useless stuff. Kernel configuration takes time. Watching videos that go through the process is good stating place. But then it needs work and experimentation. Slowly strip away things that you feel quite confident that you don't need, make things be modules as much as possible as at least the useless parts are not loaded. Mental Outlaw's video and that experimental USE flag part that I described is already quite good place. Though I might try to switch the config where you have "optimize more O2" in kernel config to "Optimize for size Os". Optimizing to size makes smaller kernel, and that might be better for CPUs with small caches. Most likely it's slightly slower that way, just saves some memory, though I would try it nonetheless because it really could be faster.
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@rockytom5889 Linux in general should be great with ancient hardware. I ran Linux on one Athlon XP machine that had nvidia chipset and AGP graphics. Though Nvidia graphics is something I haven't ever owned so can't help with that. With Gentoo you can always ask help from Gentoo IRC channel. It's really friendly place for anyone who acts respectfully.
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