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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

#21

Post by Dylan16807 »

jiggawatts wrote: post #19
anonymoushn wrote: post #13

Earlier quoted context omitted.

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 in…

Default locking every process onto a random chiplet doesn't sound like a great plan either.

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

#22

Post by Cold_Miserable »

How is the built-in Administrator account faster than a named account? I wonder if its a bloatware effect. They need to test with all bloatware removed. No control flow guard, defender, firewall, appearance to performance, no sounds, no background, microcode dll's deleted, mitigations disabled in regedit, storport disabled, every service disabled, every app deleted, edge deleted etc.

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

#23

Post by jiggawatts »

Dylan16807 wrote: post #21
jiggawatts wrote: post #19

Earlier quoted context omitted.

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 in…

Default locking every process onto a random chiplet doesn't sound like a great plan either.

AFAIK it doesn’t lock them, it just preferentially co-schedules things into a socket.

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

#24

Post by justsomehnguy »

voxic11 wrote: post #16
fuzzy2 wrote: post #12

Earlier quoted context omitted.

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.

> 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

If you somehow bypass UAC and gain the Administrators-level access then you already run with Administrator level privileges in the first place, just with a medium mandatory level.

A rope on the edge of a cliff isn't there to prevent you from falling, it's there to notify you what you should be careful. Rope works. UAC works.

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

#25

Post by fuzzy2 »

voxic11 wrote: post #16
fuzzy2 wrote: post #12

Earlier quoted context omitted.

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.

Oh, user separation is not a security boundary? I was not aware! Let’s all work as root then! /s

The fact that this was the norm on single-user Windows workstations until Windows Vista is astonishing, to say the least. How anyone could want that back is beyond me. It enabled malware to compromise the entirety of the computer with ease. No exploits or anything required! Certainly not one of these pesky UAC prompts!

Can you still shoot yourself in the foot with UAC? Yes. You own the PC. You should be able to shoot yourself in the foot, by willingly deciding to. Not accidentally.

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

#26

Post by [deleted] »

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.

[deleted]

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

#27

Post by Wowfunhappy »

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.

This is why I mentioned that the PC in question is a gaming box exclusively. There's really nothing to steal here. Maybe you could plant a virus on my network drive to leap to other computers, but that seems pretty far fetched, especially since any software is coming from that drive in the first place.

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

#28

Post by olliej »

Cold_Miserable wrote: post #22

How is the built-in Administrator account faster than a named account? I wonder if its a bloatware effect. They need to test with all bloatware removed. No control flow guard, defender, firewall, appearance to performance, no sounds, no background, microcode dll's deleted, mitigations disabled in regedit, storport disabled, every service disabled, every app deleted, edge deleted etc.

From the article it sounds like it’s a change to scheduling priorities not what is running (from other comments it sounds like there’s a change in latency related to moving processes across cores in different packages?)

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

#29

Post by Out_of_Characte »

jiggawatts wrote: post #19
anonymoushn wrote: post #13

Earlier quoted context omitted.

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 in…

Windows 'processor groups' aren't at all similar to linux NUMA aware scheduling, which is the proper method regardless, There's 64 bits that represent all cores on the system, setting those bits defines how a process is assigned to a core. The 'processor groups' is a hack that keeps the same bitmask that they originally used.

Nowadays windows can and will schedule across processor groups as per 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

#30

Post by Dylan16807 »

jiggawatts wrote: post #23
Dylan16807 wrote: post #21

Earlier quoted context omitted.

Default locking every process onto a random chiplet doesn't sound like a great plan either.

AFAIK it doesn’t lock them, it just preferentially co-schedules things into a socket.

My understanding was that a thread is only eligible to be scheduled in a single processor group at any given time, and that windows will not change the group. Is that wrong?
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