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AMD's Ryzen CPUs might be slower in PC games due to a weird Windows 11 bug

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Re: AMD's Ryzen CPUs might be slower in PC games due to a weird Windows 11 bug

#11

Post by Out_of_Characte »

tedunangst wrote: post #4

The background for this really puzzles me. AMD said you should be seeing more improvement for zen 5 over zen 4. They go back and forth, AMD says run it as super root. Zen 5 gets faster. But zen 4 gets faster too. The improvement basically disappears again when the "fix" is applied universally. So why was AMD testing with two different setups?

The phoronix bench suite showed performance in line of expectations. Its specifically games on windows that regressed. I have no clue how windows scheduler works but that can have a huge impact in games specifically.

Re: AMD's Ryzen CPUs might be slower in PC games due to a weird Windows 11 bug

#12

Post by fuzzy2 »

Wowfunhappy wrote: post #9
ChoGGi wrote: post #2

The usual consensus I've heard is that UAC is always on even after turning the slider all the way off, while using the admin account doesn't use UAC (changing the EnableLUA in reg also works).

This is the first I'm reading that UAC has a performance impact and I'd like to know more. I have a PC that I literally use for single player games and nothing else (I do not have a web browser installed, or even Steam, games are installed from a network share). I have no use for UAC and I'd like to squeeze everything out of my CPU.

If it has a performance impact, that's not on Windows but the software. Many games are really really badly made software, so that's not surprising.

UAC is the single greatest security improvement Microsoft ever created.

Re: AMD's Ryzen CPUs might be slower in PC games due to a weird Windows 11 bug

#13

Post by anonymoushn »

Out_of_Characte wrote: post #11
tedunangst wrote: post #4

The background for this really puzzles me. AMD said you should be seeing more improvement for zen 5 over zen 4. They go back and forth, AMD says run it as super root. Zen 5 gets faster. But zen 4 gets faster too. The improvement basically disappears again when the "fix" is applied universally. So why was AMD testing with two different setups?

The phoronix bench suite showed performance in line of expectations. Its specifically games on windows that regressed. I have no clue how windows scheduler works but that can have a huge impact in games specifically.

Compared to Zen4, Zen5 has much higher latency between cores on different chiplets. It's possible that a scheduler + app combo could regress on Zen5 for this reason. It sounds basically impossible for single-threaded apps to be impacted because timeslices are really big. Multithreaded apps where threads are communicating constantly could easily run slower if the scheduler sees all the cores as identical and interchangeable.

I don't know much about this topic, but it seems like Windows uses Processor Groups for scheduling[0], and generally tries to fit each NUMA node into 1 Processor Group (as long as it has at most 64 cores in it). Since the issue here is latency between chiplets and no NUMA is involved, all the cores go in the same Processor Group.

[0]: https://learn.microsoft.com/en-us/windows/win32/procthread/p...

Re: AMD's Ryzen CPUs might be slower in PC games due to a weird Windows 11 bug

#14

Post by dathinab »

tedunangst wrote: post #4

The background for this really puzzles me. AMD said you should be seeing more improvement for zen 5 over zen 4. They go back and forth, AMD says run it as super root. Zen 5 gets faster. But zen 4 gets faster too. The improvement basically disappears again when the "fix" is applied universally. So why was AMD testing with two different setups?

my guess is there is a bug in Windows related to scheduling which makes Zen 5 slower and by using the admin accounts for testing but comparing to Zen 4 tests results without admin account it was obfuscated.

I mean on Linux Zen 5 seems to be clearly faster then Zen 4 by a good margin.

Re: AMD's Ryzen CPUs might be slower in PC games due to a weird Windows 11 bug

#15

Post by NavinF »

ZoomerCretin wrote: post #10
ChoGGi wrote: post #2

The usual consensus I've heard is that UAC is always on even after turning the slider all the way off, while using the admin account doesn't use UAC (changing the EnableLUA in reg also works).

Is there any good reason for Microsoft to not open-source Windows? They are dangerously close to creating the Year of the Linux Desktop if they continue proving Wirth right.

> They are dangerously close to creating the Year of the Linux Desktop

How much do you wanna bet? I don't see that happening in the next decade

Re: AMD's Ryzen CPUs might be slower in PC games due to a weird Windows 11 bug

#16

Post by voxic11 »

fuzzy2 wrote: post #12
Wowfunhappy wrote: post #9

Earlier quoted context omitted.

This is the first I'm reading that UAC has a performance impact and I'd like to know more. I have a PC that I literally use for single player games and nothing else (I do not have a web browser installed, or even Steam, games are installed from a network share). I have no use for UAC and I'd like to squeeze everything out of my CPU.

If it has a performance impact, that's not on Windows but the software. Many games are really really badly made software, so that's not surprising. UAC is the single greatest security improvement Microsoft ever created.

UAC is not a security boundary. Its only there to prevent the user from accidentally making changes to the system that they didn't intend, but it provides no security except from your own mistakes. Its so much not considered a security boundary that microsoft doesn't even offer a bug bounty for UAC bypasses.

Re: AMD's Ryzen CPUs might be slower in PC games due to a weird Windows 11 bug

#17

Post by Rohansi »

Out_of_Characte wrote: post #11
tedunangst wrote: post #4

The background for this really puzzles me. AMD said you should be seeing more improvement for zen 5 over zen 4. They go back and forth, AMD says run it as super root. Zen 5 gets faster. But zen 4 gets faster too. The improvement basically disappears again when the "fix" is applied universally. So why was AMD testing with two different setups?

The phoronix bench suite showed performance in line of expectations. Its specifically games on windows that regressed. I have no clue how windows scheduler works but that can have a huge impact in games specifically.

Maybe something to do with Game Mode on Windows.

Re: AMD's Ryzen CPUs might be slower in PC games due to a weird Windows 11 bug

#19

Post by jiggawatts »

anonymoushn wrote: post #13
Out_of_Characte wrote: post #11

Earlier quoted context omitted.

The phoronix bench suite showed performance in line of expectations. Its specifically games on windows that regressed. I have no clue how windows scheduler works but that can have a huge impact in games specifically.

Compared to Zen4, Zen5 has much higher latency between cores on different chiplets. It's possible that a scheduler + app combo could regress on Zen5 for this reason. It sounds basically impossible for single-threaded apps to be impacted because timeslices are really big. Multithreaded apps where threads are communicating constantly could easily run slower if the scheduler sees all the cores as identical and interchan…

This sounds like a trivial fix: put the two chiplets into separate processor groups, because that's effectively what they are.

This feature was originally about non-uniform memory access (NUMA), but effectively it is "core-to-socket" mapping. If a processor has chiplets on it, then it's effectively sockets-within-sockets. The software needs just a minor update to consider the chiplets to be the scheduling boundary instead of the AM5 socket.

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