Tuesday, October 12th 2021

First Windows 11 Patch Tuesday Makes Ryzen L3 Cache Latency Worse, AMD Puts Out Fix Dates

by
btarunr
 Discuss (157 Comments)
Microsoft on October 12 put out the first Cumulative Updates for the new Windows 11 operating system, since its October 5 release. The company's monthly update packages for Windows are unofficially dubbed "patch Tuesday" updates, as they're scheduled to come out on the second Tuesday of each month. Shortly after Windows 11 launch, AMD and Microsoft jointly discovered that Windows 11 is poorly optimized for AMD Ryzen processors, which see significantly increased L3 cache latency, and the UEFI-CPPC2 (preferred cores mechanism) rendered not working. In our own testing, a Ryzen 7 2700X "Pinnacle Ridge" processor, which typically posts an L3 cache latency of 10 ns, was tested to show a latency of 17 ns. This was made much worse with the October 12 "patch Tuesday" update, driving up the latency to 31.9 ns.

AMD put out a statement on social media, which surfaced on Reddit. The company stated that patches for the two issues have been developed, and specified dates on which they'll be released. The patch for the Preferred Cores (UEFI-CPPC2) bug will be released on October 21. Customers can request the patch even earlier. By "customers," AMD is probably referring to big enterprise customers running mission-critical applications on Threadripper or EPYC-powered workstations. The L3 cache latency bug will be fixed through the Windows Update channel, its release is scheduled for October 19.
If rumors surrounding the late-October/early-November launch dates of 12th Gen Intel Core "Alder Lake" processors are true, then the situation with these patches will have a direct impact on AMD. Processor reviewers will be compelled to use Windows 11 for their Core "Alder Lake" testing, as the new operating system supposedly has greater awareness of the heterogeneous core design. The switch to Windows 11 will force a re-bench of all processors, including the AMD Ryzen chips. With AMD cautioning of an up to 15% performance hit from the added cache latency and Preferred Cores bugs, results of AMD processors in 12th Gen Core launch reviews could be affected. It is advisable for AMD to reach out to the press with these patches immediately, if they are ready.
Source: destiny2sk (Reddit)

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157 Comments on First Windows 11 Patch Tuesday Makes Ryzen L3 Cache Latency Worse, AMD Puts Out Fix Dates

#101
phanbuey
bugI see. I was thinking Microsoft tried to put everything under the same umbrella and somehow messed up AMD support. But if support is still separated, it's really weird they messed it up. I mean, it was already done for Win10. Then again, I'm a software developer, this isn't the weirdest thing I have seen.
I'm sure it's security 'feature' related.

I think most of performance hits from windows these days is coming from new security features (vbs, flow control, memory randomization, blah blah). When you're babysitting how every piece of memory is being accessed/allocated this is bound to happen.
Posted on Reply
#102
zlobby
phanbueyI'm sure it's security 'feature' related.

I think most of performance hits from windows these days is coming from new security features (vbs, flow control, memory randomization, blah blah). When you're babysitting how every piece of memory is being accessed/allocated this is bound to happen.
Until hardware is fully capable of running everything virtualized natively, we're bound for such 'hybrid' solutions where parts of the virtualization is done in software, while the rest is done in hardware.

Hopefully the day every program runs completely isolated natively, in hardware will be upon us all soon. It also begs the question what will happen when a sufficiently advanced (self-aware) AI manage to obfuscate its real goals with these neat security features?
Posted on Reply
#103
bug
zlobbyUntil hardware is fully capable of running everything virtualized natively, we're bound for such 'hybrid' solutions where parts of the virtualization is done in software, while the rest is done in hardware.

Hopefully the day every program runs completely isolated natively, in hardware will be upon us all soon. It also begs the question what will happen when a sufficiently advanced (self-aware) AI manage to obfuscate its real goals with these neat security features?
What does that even mean?
Posted on Reply
#104
phanbuey
zlobbyUntil hardware is fully capable of running everything virtualized natively, we're bound for such 'hybrid' solutions where parts of the virtualization is done in software, while the rest is done in hardware.

Hopefully the day every program runs completely isolated natively, in hardware will be upon us all soon. It also begs the question what will happen when a sufficiently advanced (self-aware) AI manage to obfuscate its real goals with these neat security features?
Horizon Zero Dawn. :D
Posted on Reply
#105
lexluthermiester
bugI was thinking Microsoft tried to put everything under the same umbrella and somehow messed up AMD support.
The way I understand it, there's a bit of truth there. The new scheduling schemes are a part of the base changes being made to 11, but those changes apply equally to all CPU models. Where the glitch comes in is where those processes interact with the architecture of each CPU line. Ryzen CPU's are a built in a unique way and as such, the CPU driver code has to be written to accommodate how it works.

What likely happened was microsoft give AMD the specifications of the changes they were going to make and AMD delivered back code for microsoft to integrate, then along the way something was changed and the code AMD created no longer worked properly. However, that's just a guess based on what I've been able to discover thus far.
Posted on Reply
#106
zlobby
phanbueyHorizon Zero Dawn. :D
Deragnement much?
bugWhat does that even mean?
What indeed?
Posted on Reply
#107
R-T-B
lexluthermiesterNope. This has nothing to do with Intel. AMD's CCX Complex/Infinity Fabric works in a way that is very different and unrelated to how Intels big/little scheme works. Each have CPU Kernel driver code and they are mutually exclusive.

The Kernel driver code for each CPU does not and can not interfere with the code of another.
But the scheduler can. I have a feeling what happened is there rather than kernel.
Posted on Reply
#108
phanbuey
zlobbyDeragnement much?
The story of HZD is an ai that wraps itself in encryption that can't be broken/shut down.

Edit: totally missed it the first time :D...
Posted on Reply
#109
zlobby
phanbueySpelling much?

The story of HZD is an ai that wraps itself in encryption that can't be broken/shut down.
Ah, I did forget the quotes on 'Derangement'. And I misspelt it, too. You ought to know it's in the game's synopsis, no?
Posted on Reply
#110
lexluthermiester
R-T-BBut the scheduler can. I have a feeling what happened is there rather than kernel.
You might be right. I'll be honest, this is just a guess based on the info available. That level of programming is way beyond my pay grade.
Posted on Reply
#112
Mussels
Freshwater Moderator
lexluthermiesterYou also didn't see them announce updated support for each gen of Ryzen nor 8th, 9th, 10th &11th gen Core series CPU's from Intel, but they did. Those updates will come in an update as per usual.


Maybe? Common sense really..
No, really. Alder lake requires windows 11.

It's two different CPU architectures in one, Win 10 would throw crysis on the low performance core and minesweeper on the big ones

The fix is live on the beta channel

Posted on Reply
#113
lexluthermiester
MusselsNo, really. Alder lake requires windows 11.
Are you sure? Might be mistaken but I don't remember reading Alderlake being exclusive to Win11...
Posted on Reply
#114
Mussels
Freshwater Moderator
lexluthermiesterAre you sure? Might be mistaken but I don't remember reading Alderlake being exclusive to Win11...
You might get it to work. It wont work properly.

It's like asking why hyperthreading doesnt work in DOS, because the OS isn't coded for it.

Microsoft and intel decided to make Alder lake only work properly on windows 11.
No one knows if that means a performance hit, missing cores, etc - yet.

This crap is not coming to 10:
Posted on Reply
#115
lexluthermiester
MusselsYou might get it to work. It wont work properly.

It's like asking why hyperthreading doesnt work in DOS, because the OS isn't coded for it.

Microsoft and intel decided to make Alder lake only work properly on windows 11.
No one knows if that means a performance hit, missing cores, etc - yet.

This crap is not coming to 10:
Ok, I see what you're getting at. Intel saying that it is "specifically designed for Windows 11" does not directly state exclusivity for that OS. It might hint at it, but until they actually make that direct statement, it's not set in stone..
Posted on Reply
#116
Mussels
Freshwater Moderator
lexluthermiesterOk, I see what you're getting at. Intel saying that it is "specifically designed for Windows 11" does not directly state exclusivity for that OS. It might hint at it, but until they actually make that direct statement, it's not set in stone..
They repeatedly say it'll perform crap in any OS that is not specifically patched for the new big.little design
As far as any reviewer or consumer is concerned, thats an exclusive, since 11 is the only OS they (intel) have worked with.

It's like saying a 5950x is supported in DOS... sure, but it's sure as fuck not at full performance.
Posted on Reply
#117
Selaya
just disable the little cores then, nothing of value was lost anyways so
Posted on Reply
#118
lexluthermiester
MusselsThey repeatedly say it'll perform crap in any OS that is not specifically patched for the new big.little design
As far as any reviewer or consumer is concerned, thats an exclusive, since 11 is the only OS they've worked with.

It's like saying a 5950x is supported in DOS... sure, but it's sure as fuck not at full performance.
Not trying to ruffle your feathers. It seems like they just don't have things ironed out yet. This might be because of market adoption for Windows 11, which hasn't taken off like a shot or a number of other factors.
Posted on Reply
#119
zlobby
lexluthermiesterNot trying to ruffle your feathers.
But his jimmies were rustlesd. :D
Posted on Reply
#120
windwhirl
Selayajust disable the little cores then, nothing of value was lost anyways so
If I buy big and small cores, I'm gonna use all of them.
Posted on Reply
#121
lexluthermiester
windwhirlIf I buy big and small cores, I'm gonna use all of them.
That's a reasonable expectation.
Posted on Reply
#122
ThrashZone
windwhirlIf I buy big and small cores, I'm gonna use all of them.
Hi,
Little cores likely will be hot potato's lol
Posted on Reply
#124
Selaya
windwhirlIf I buy big and small cores, I'm gonna use all of them.
thats on you then
i would only ever buy big cores but idt there's an 8/0 SKU?
so i get unwanted useless little cores shoved down my throat, that don't even want to play nice w/ all OSes so yeah, -> disable
Posted on Reply
#125
R-T-B
Selayathats on you then
i would only ever buy big cores but idt there's an 8/0 SKU?
so i get unwanted useless little cores shoved down my throat, that don't even want to play nice w/ all OSes so yeah, -> disable
This is why options are nice.
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