It's also because around 20 years ago there was a "reset" when we switched from x86 to x86_64. When AMD introduced x86_64, it made a bunch of the previously optional extension (SSE up to a certain version etc) a mandatory part of x86_64. Gentoo systems could already be optimized before on x86 using those instructions, but now (2004ish) every system using x86_64 was automatically always taking full advantage of all of these instructions*.

Since then we've slowly started accumulating optional extensions again; newer SSE versions, AVX, encryption and virtualization extensions, probably some more newfangled AI stuff I'm not on top of. So very slowly it might have started again to make sense for an approach like Gentoo to exist**.

* usual caveats apply; if the compiler can figure out that using the instruction is useful etc.

** but the same caveats as back then apply. A lot of software can't really take advantage of these new instructions, because newer instructions have been getting increasingly more use-case-specific; and applications that can greatly benefit from them will already have alternative code-pathes to take advantage of them anyway. Also a lot of the stuff happening in hardware acceleration has moved to GPUs, which have a feature discovery process independent of CPU instruction set anyway.

FWIW the cool thing about gentoo was the "use-flags", to enable/disable compile-time features in various packages. Build some apps with GTK or with just the command-line version, with libao or pulse-audio, etc. Nowadays some distro packages have "optional dependencies" and variants like foobar-cli and foobar-gui, but not nearly as comprehensive as Gentoo of course. Learning about some minor custom CFLAGS was just part of the fun (and yeah some "funroll-loops" site was making fun of "gentoo ricers" way back then already).

I used Gentoo a lot, jeez, between 20 and 15 years ago, and the install guide guiding me through partitioning disks, formatting disks, unpacking tarballs, editing config files, and running grub-install etc, was so incredibly valuable to me that I have trouble expressing it.

This should build a lot more incentive for compiler devs to try and use the newer instructions. When everyone uses binaries compiled without support for optional instruction sets, why bother putting much effort into developing for them? It’ll be interesting to see if we start to see more of a delta moving forward.

According to this[0] study of the Ubuntu 16.04 package repos, 89% of all x86 code was instructions were just 12 instructions (mov, add, call, lea, je, test, jmp, nop, cmp, jne, xor, and -- in that order).

The extra issue here is that SIMD (the main optimization) simply sucks to use. Auto-vectorization has been mostly a pipe dream for decades now as the sufficiently-smart compiler simply hasn't materialized yet (and maybe for the same reason the EPIC/Itanium compiler failed -- deterministically deciding execution order at compile time isn't possible in the abstract and getting heuristics that aren't deceived by even tiny changes to the code is massively hard).

Doing SIMD means delving into x86 assembly and all it's nastiness/weirdness/complexity. It's no wonder that devs won't touch it unless absolutely necessary (which is why the speedups are coming from a small handful of super-optimized math libraries). ARM vector code is also rather Byzantine for a normal dev to learn and use.

We need a more simple assembly option that normal programmers can easily learn and use. Maybe it's way less efficient than the current options, but some slightly slower SIMD is still going to generally beat no SIMD at all.

[0] https://oscarlab.github.io/papers/instrpop-systor19.pdf

I somehow have the memory that there was an extremely narrow time window where the speedup was tangible and quantifiable for Gentoo, as they were the first distro to ship some very early gcc optimisation. However it's open source software so every other distro soon caught up and became just as fast as Gentoo.

Would it make a difference if you compile the whole system vs. just the programs you want optimized?

As in, are there any common libraries or parts of the system that typically slow things down, or was this more targeting a time when hardware was more limited so improving all would have made things feel faster in general.

If every computer built in the last decade gets 1% faster and all we have to pay for that is a bit of one-off engineering effort and a doubling of the storage requirement of the ubuntu mirrors that seems like a huge win

If you aren't convinced by your ubuntu being 1% faster, consider how many servers, VMs and containers run ubuntu. Millions of servers using a fraction of a percent less energy multiplies out to a lot of energy

You need 100 servers. Now you need to only buy 99. Multiply that by a million, and the economies of scale really matter.

A lott of improvements are very incremental. In agregate, they often compound and are vey significant.

If you would only accept 10x improvements, I would argue progress would be very small.

It's rarely going to be worth it for an individual user, but it's very useful if you can get it to a lot of users at once. See https://www.folklore.org/Saving_Lives.html

"Well, let's say you can shave 10 seconds off of the boot time. Multiply that by five million users and thats 50 million seconds, every single day. Over a year, that's probably dozens of lifetimes. So if you make it boot ten seconds faster, you've saved a dozen lives. That's really worth it, don't you think?"

I put a lot of effort into chasing wins of that magnitude. Over a huge userbase, something like that has a big positive ROI. These days it also affects important things like heat and battery life.

The other part of this is that the wins add up. Maybe I manage to find 1% every couple of years. Some of my coworkers do too. Now you're starting to make a major difference.

They did say some packages were more. I bet some are 5%, maybe 10 or 15. Maybe more.

Well one example could be llama.cpp . It's critical for them to use every single extension the CPU has move more bits at a time. When I installed it I had to compile it.

This might make it more practical to start offering OS packages for things like llama.cpp

I guess people that don't have newer hardware aren't trying to install those packages. But maybe the idea is that packages should not break on certain hardware.

Blender might be another one like that which really needs the extensions for many things. But maybe you so want to allow it to be used on some oldish hardware anyway because it still has uses that are valid on those machines.

it's very no uniform. 99% see no change, but 1% see 1.5-2x better performance

   > Previous benchmarks (...) show that most packages show a slight (around 1%) performance improvement and some packages, mostly those that are somewhat numerical in nature, improve more than that.

> Are there any use cases where that 1% is worth any hassle whatsoever?

I don't think this is a valid argument to make. If you were doing the optimization work then you could argue tradeoffs. You are not, Canonical is.

Your decision is which image you want to use, and Canonical is giving you a choice. Do you care about which architecture variant you use? If you do, you can now pick the one that works best for you. Do you want to win an easy 1% performance gain? Now you have that choice.

  > where that 1% is worth any hassle

You'll need context to answer your question, but yes there are cases.

Let's say you have a process that takes 100hrs to run and costs $1k/hr. You save an hour and $1k every time you run the process. You're going to save quite a bit. You don't just save the time to run the process, you save literal time and everything that that costs (customers, engineering time, support time, etc).

Let's say you have a process that takes 100ns and similarly costs $1k/hr. You now run in 99ns. Running the process 36 million times is going to be insignificant. In this setting even a 50% optimization probably isn't worthwhile (unless you're a high frequency trader or something)

This is where the saying "premature optimization is the root of all evil" comes from! The "premature" part is often disregarded and the rest of the context goes with it. Here's more context to Knuth's quote[0].

  There is no doubt that the holy grail of efficiency leads to abuse. Programmers waste enormous amounts of time thinking about, or worrying about, the speed of noncritical parts of their programs, and these attempts at efficiency actually have a strong negative impact when debugging and maintenance are considered. We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil.

  Yet we should not pass up our opportunities in that critical 3%. A good programmer will not be lulled into complacency by such reasoning, he will be wise to look carefully at the critical code; but only after that code has been identified.

Knuth said: "Get a fucking profiler and make sure that you're optimizing the right thing". He did NOT say "don't optimize".

So yes, there are plenty of times where that optimization will be worthwhile. The percentages don't mean anything without the context. Your job as a programmer is to determine that context. And not just in the scope of your program, but in the scope of the environment you expect a user to be running on. (i.e. their computer probably isn't entirely dedicated to your program)

[0] https://dl.acm.org/doi/10.1145/356635.356640 (alt) https://sci-hub.se/10.1145/356635.356640

Anything at scale. 1% across FAANG is huge.

> some packages, mostly those that are somewhat numerical in nature, improve more than that

Perhaps if you're doing CPU-bound math you might see an improvement?

Any hyperscaler will take that 1% in a heartbeat.

Very few people are in the situation where this would matter.

Standard advice: You are not Google.

I'm surprised and disappointed 1% is the best they could come up with, with numbers that small I would expect experimental noise to be much larger than the improvement. If you tell me you've managed a 1% improvement you have to do a lot to convince me you haven't actually made things 5% worse.

Aggregated metrics are always useless as they tend to show interesting and sometimes exciting data that in actuality contains zero insight. I'm always weary of people making decisions based on aggregate metrics.

Would be nice to know the per app metrics.

At least Intel and AMD have settled on a mutually supported subset of AVX-512 instructions.

What you said is correct wrt. official support, but Debian also has an unofficial ports infrastructure that could be repurposed towards enabling Debian for older architecture variants.

I wonder how this relates to Intel's "One API", which extends a single C code base across the various CPU targets (such as the core ALU, base vector units, AVX-512, NPU) and Intel GPU accelerators.

Not the same thing, or perhaps an augmentation of Intel performance libraries (which required C++, I believe).

Sure, harmonizing all of this may have suggested that there were too many software teams. But device drivers don't write themselves, and without feedback from internal software developers, you can't validate your CPU designs.

OTOH, you can remove the runtime dispatching logic entirely if you compile separate binaries for each architecture variant.

Especially the binaries for the newest variant, since they can entirely conditionals/branching for all older variants.