Ubuntu 25.04 "Plucky Puffin" Development Opens - Defaulting To -O3 Optimizations

[patrick1946]

More often then not, I see a significant speed increase with my Intel CPUs on my popular architectures.

Maybe this so-called slowdown while executing branches is more typically seen with non-Intel CPUs, or other CPUs, or certain architectures. Almost all slow-downs I do see, are the initial load times of the executable file(s) being slightly larger, and typically not while the binary is executing it's functions.

On the flip, I more so see bug or segfaults, again particularly due to likely poorly written or poorly maintained code.

Seems I'm only getting part of the story with all of these stated slow-downs. Shrugs...

Another possibility is the design and build quality of the computer platforms. Typically I build and invest in platforms built like a tank, with only having to upgrade every decade or more, except for my laptops. Still, my laptop(s) typically perform very well with O3 optimizations.

Another idea, maybe people do not want to see de facto Linux distributions running as quickly as Apple and Windows, as I believe those operating system platforms are compiled with optimizations. Again, shrugs...

I still strongly believe some Linux distributions should invest in O3 optimizations. I ran Gentoo for decades with O3 optimizations with few problems.

Seems your hardware is quite old. O3 is unrolling aggressively which has an advantage with not so good branch predictor. With modern branch predictors it can be the other way around.

[rogerx]

Instruction size is not about loading but execution. If it fills your caches with to much instructions you get more cache misses. And that is slowing down the execution.

O3 is aggressively unrolling but with modern branch predictors that can be counter productive.

You can see that in benchmarks, O3 has no big advantage and can be even slower. It all depends on the CPU and the program.

More often then not, I see a significant speed increase with my Intel CPUs on my popular architectures.

Maybe this so-called slowdown while executing branches is more typically seen with non-Intel CPUs, or other CPUs, or certain architectures. Almost all slow-downs I do see, are the initial load times of the executable file(s) being slightly larger, and typically not while the binary is executing it's functions.

On the flip, I more so see bug or segfaults, again particularly due to likely poorly written or poorly maintained code.

Seems I'm only getting part of the story with all of these stated slow-downs. Shrugs...

Another possibility is the design and build quality of the computer platforms. Typically I build and invest in platforms built like a tank, with only having to upgrade every decade or more, except for my laptops. Still, my laptop(s) typically perform very well with O3 optimizations.

Another idea, maybe people do not want to see de facto Linux distributions running as quickly as Apple and Windows, as I believe those operating system platforms are compiled with optimizations. Again, shrugs...

I still strongly believe some Linux distributions should invest in O3 optimizations. I ran Gentoo for decades with O3 optimizations with few problems.

[patrick1946]

You're likely correct. If I'm not mistaken, when using O2 versus O3, there maybe a longer load time, but overall the application will perform quicker.

Rarely, if ever, have a witnessed an application reacting slower with O3, if anything difference, reacting the same if not, reacting by far quicker.

Instruction size is not about loading but execution. If it fills your caches with to much instructions you get more cache misses. And that is slowing down the execution.

O3 is aggressively unrolling but with modern branch predictors that can be counter productive.

You can see that in benchmarks, O3 has no big advantage and can be even slower. It all depends on the CPU and the program.

[rogerx]

Long ago I believe -O3 enabled --no-strict-aliasing which caused bugs when used to compile code that had aliased variables. The code was not wrong.

Most times, I've witnessed compilation statements emitting warnings.

Code compiling fine does not necessarily mean the code was written correctly.

[rogerx]

Wow, do you really think the compiler has no bugs? O3 is producing more machine code, which has the disadvantage of filling the caches. So, in the end, O3 can be slower than Os. Modern hardware does not profit so much from unrolling because the branch prediction has improved.

You're likely correct. If I'm not mistaken, when using O2 versus O3, there maybe a longer load time, but overall the application will perform quicker.

Rarely, if ever, have a witnessed an application reacting slower with O3, if anything difference, reacting the same if not, reacting by far quicker.

[sbivol]

Stop feeding it, please.

[F.Ultra]

No, wait a water rat. Come on the order. I have not yet installed the Ubuntu and did not check all the ports. I think there are open ones. Because the Sharing Desktop application in Ubuntu 16.04 uses a VNC protocol for remote access to your desktop, and by default it opens certain ports for incoming connections. This is only the beginning.

No there are no open ports by default for desktop sharing or for any other forms of remote access/administration. Are you really confused on the concept of default vs you actively enabling/starting/installing something?

[F.Ultra]

Let's clarify something else. I'm not a developer. I am a simple user. You are called a professional. You don't even know what is installed in Ubuntu. For the first time you hear about Sharing Decktop. You were sharply bored. I lost my time to find all this. You started an investigation and organized everything, as if I were lying. You wanted to put me a liar. All this is a place, and even worse. You went to shit. I demand apologies.

Yes huge mistake for me not keeping track that Ubuntu had this setting not in the general settings but left to the application itself 8 years ago... Not sure why you want me to apologize to you for proving that you where lying this whole time?

The only reason I started to investigate this was to make sure that I was correct and not remembering it wrongly, that is what you do if you are serious instead of just writing pure nonsense like some one else have done here in post after post.

As far as I'm concerned this is now a closed case and an established fact that you lied from the beginning to the end.

[F.Ultra]

Water rat, I've already found a picture

ok so that window is not from the Ubuntu settings (which is why I didn't find it) but the window for the vino-server application. And that is disabled by default (just checked on the fresh install I did earlier today of 16.04 and "Allow other users to view your desktop" is unchecked which also is why the port isn't opened. So you have deliberately enabled this yet complain here that this is the default. Aka you are not in any position to sling personal insults.

[F.Ultra]

animals, I have to download Ubuntu 16 again. There are applications for remote access to the desktop. No matter what you say, but it was. The Internet speed is low.

Oh there are applications to download to set that up, but you (and we) are talking about defaults here.