Windows 10 Scheduler bug causes poor RyZen performance

[Space Reptile]

sauce: http://wccftech.com/amd-ryzen-performance-negatively-affected-windows-10-scheduler-bug/

 

 

there is currently an issue w/ the scheduler in windows 10 , as It sees all threads on Ryzen as cores it runs into issues ,

this might explain why the cpu seems to perform better in some applications when SMT is enabled

 

to quote the article

Quote

Not All Threads Are Created Equal

Windows 10′ scheduler correctly identifies Intel’s hyper-threads as lesser performing than principal core threads and schedules tasks in a way that’s takes advantage of the additional throughput without negatively impacting performance. Unfortunately the scheduler currently is not able to differentiate principal core threads from virtual SMT threads with Ryzen and in fact sees 16 thread Ryzen 7 processors as processors with 16 physical cores with equal resources per thread.

Because it does not give any preferential prioritization of scheduling tasks to primary threads over SMT threads like it does on Intel platforms, a massively larger percentage of tasks can and do end up getting scheduled for a virtual SMT thread rather than a principal core thread. Resulting in significant artificial performance degradation.

(I know its WCCF , but nobody else wrote an article about it and they said that its a thing on twitter , as seen in the picture)

[LegendKillerRG]

Basically the real cores of threads aren't being used effectively but rather just spread workload onto all 16 threads.. isn't the extra thread meant to be so that it utilizes the cores more efficiently. Like a core is split into two thread and one handle 50% while the other thread handle 50%, and at 25% for two threads is like 25% on one core..

[Space Reptile]

2 minutes ago, LegendKillerRG said:

Basically the real cores of threads aren't being used effectively but rather just spread workload onto all 16 threads.. isn't the extra thread meant to be so that it utilizes the cores more efficiently. Like a core is split into two thread and one handle 50% while the other thread handle 50%, and at 25% for two threads is like 25% on one core..

no , it gives single threaded applications that need more performance a thread by accident , and as we all know threads don't come close to the performance of a real core , it can also happen that a 2/4 threaded application gets given 3 threads and one real core , hurting overall performance

[Morgan MLGman]

This has been known for a while now, but it's good to know that Microsoft is aware of the issue and working on a fix.

 

zMeul will probably still say the scheduler is fine and it's "Zendozer's" fault

 

EDIT:

37 minutes ago, Space Reptile said:

sauce: http://wccftech.com/amd-ryzen-performance-negatively-affected-windows-10-scheduler-bug/

(I know its WCCF , but nobody else wrote an article about it and they said that its a thing on twitter , as seen in the picture)

Just noticed this is also from WCCFtech, why does nobody listen to me and it's still not an obligation on this forum to put a [WCCFTech "Info"] tag before posting "news"  from this site ;-; It could help keep some people from spreading unnecessary bullshit all over the internet.

[Space Reptile]

6 minutes ago, Morgan MLGman said:

zMeul will probably still say the scheduler is fine and it's "Zendozer's" fault

im surprised Zm didn't compare Zen to the Hindenburg yet , the architecture is called zeppelin

 

Quote

Just noticed this is also from WCCFtech, why does nobody listen to me and it's still not an obligation on this forum to put a [WCCFTech "Info"] tag before posting "news"  from this site ;-;

yea I know , there is a reason why I put a disclaimer there , on stuff like r/Amd WCCF is already banned

[yian88]

Stop dreaming and hope threads, ryzen just isnt as good in IPC for gaming and they failed to have a smooth launch because of memory/BIOS issues.

Ryzen wont get better, because x86 cpu's are not gpu-s, they dont have drivers with millions of lines of codes and possibility to optimize drivers for each app/game.

Its either good since day one or it isnt. New bios might help with memory and windows fix with SMT a bit but thats it, the IPC will stay the same, and nothing changes the fact that the silicon from globalfoundries used in zen is complete garbage cant even OC at all.

They really need to make Zen+ release in mid 2018 and fix all the problems + better IPC for games and better silicon for OC.

[LAwLz]

This does not confirm anything... Even if there is some bug in the scheduler (Microsoft's twitter support just said they would look into it) we still don't know how much of a performance increase it will bring. Again, back when Bulldozer got its fix the performance only increased by 1-2%. Don't expect huge performance gains because it most likely will not happen, and it especially won't bring the Ryzen 7 on-par with the 7700K for gaming.

[Morgan MLGman]

10 minutes ago, LAwLz said:

This does not confirm anything... Even if there is some bug in the scheduler (Microsoft's twitter support just said they would look into it) we still don't know how much of a performance increase it will bring. Again, back when Bulldozer got its fix the performance only increased by 1-2%. Don't expect huge performance gains because it most likely will not happen, and it especially won't bring the Ryzen 7 on-par with the 7700K for gaming.

Well, considering that with SMT disabled you get up to 20% performance more in some games then it won't be lower than this value. So it's pretty much: any performance gains from having SMT disabled in specific games will be the lowest value that the scheduler fix should bring for the SMT-on setting.

 

17 minutes ago, yian88 said:

Stop dreaming and hope threads, ryzen just isnt as good in IPC for gaming and they failed to have a smooth launch because of memory/BIOS issues.

Ryzen wont get better, because x86 cpu's are not gpu-s, they dont have drivers with millions of lines of codes and possibility to optimize drivers for each app/game.

Its either good since day one or it isnt. New bios might help with memory and windows fix with SMT a bit but thats it, the IPC will stay the same, and nothing changes the fact that the silicon from globalfoundries used in zen is complete garbage cant even OC at all.

They really need to make Zen+ release in mid 2018 and fix all the problems + better IPC for games and better silicon for OC.

Well, you're just wrong here so stay within your unrealistic world. If you don't know what you're talking about, this post may just as well be classified as spam.

[SpaceGhostC2C]

51 minutes ago, LegendKillerRG said:

Basically the real cores of threads aren't being used effectively but rather just spread workload onto all 16 threads.. isn't the extra thread meant to be so that it utilizes the cores more efficiently. Like a core is split into two thread and one handle 50% while the other thread handle 50%, and at 25% for two threads is like 25% on one core..

You have to understand that CPUs dont' have threads, they have cores. When you read a CPU is "4C/8T", it simply means each of its cores will accept 2 tasks (or "threads") at once, i.e., it won't show up as "busy" after receiving only one. However, in terms of hardware there's still one core to do all the job. It's often said informally that "the CPU has X threads", but it is more accurate to say that it "accpets X threads", as it is not a hardware resource, but just a way to use the existing one. Programs are the ones having threads: a given program may create 1, 2, 37, any number of threads, and the OS will assign them to cores, either physical or logical, based on some rules.

 

The reason why SMT can be a good idea is because a given task may not need to use all the capabilities inside a core. Hence, while the core is "busy", some of its internal components aren't really doing much. Hence, it is possible for a different thread to utilize those idle parts, as long as it needs them before needing what the first thread is using. That's why the benefits of SMT vary from application to application: when the two tasks require very different things from the CPU, or  require varying intensities of each of the core capabilities during its execution, the benefits are higher, as there are many "idle times" to exploit (example: heavy multitasking of light applications). On the other hand, when the tasks are identical and require the use of all capabilities, or constant use of a given one throughout their execution, SMT is at best useless and at worst counter-productive (for example, parallel computing).

 

The takeout from the previous paragraph is: it's always better to run 1 thread per core until you run out of cores, and only then try to see if you can squeeze a little more work from any unnecessary within-core idle resources, if any.

Bulldozer had a similar problem, although in that case moste of the hardware is duplicated inside a module, hence the gains from doing it right weren't as high. Still, a patch was needed to make sure that Windows used one core per module before re-using the same module again, mitigating the effect of the bottlenecks that can occur inside a module. For an HT / SMT CPU, where there's basically no duplicated hardware, doing it right is much more important.

[SpaceGhostC2C]

11 minutes ago, LAwLz said:

 Again, back when Bulldozer got its fix the performance only increased by 1-2%.

Bulldozer had two physical cores with shared resources, not one core shared 100% by two threads running on it. You can play with affinities in any hyperthreaded CPU to see what kind of difference can it make to poorly assign tasks to cores (which of course depends on the tasks as well).

[Space Reptile]

9 hours ago, LAwLz said:

This does not confirm anything... Even if there is some bug in the scheduler we still don't know how much of a performance increase it will bring

running a game on a proper core instead of a thread wont give a performance increase , shure bud

9 hours ago, LAwLz said:

back when Bulldozer

>comparing bulldozer w/ zen

 

9 hours ago, LAwLz said:

won't bring the Ryzen 7 on-par with the 7700K for gaming.

unless games use more cores/ threads the better IPC will always win

 

it wasn't meant to compete w/ the 77k to begin w/ , and yes you get lower fps in games

but in games like BF1 the 77k is pegged when running for max fps while the R7 is at like 40% usage

yet the difference in FPS is less than 10%.

it shows that the R7 has a lot more headroom , but games cant use it

that's why the 6900 sucks in games as well , no game uses more than 6 threads

the R7 is a productivity chip look at blender / cinebench / handbrake and so on , it comes close to the 69k or even beats it , while costing a lot less

 

this fix will give you more performance because as I already said , lesser threaded applications get assigned less powerful threads instead of the more powerful cores by accident because 10 cant tell the difference , it WILL improve performance by default , not 70% , not 50% but you can look at something like 10%

Edited March 9, 2017 by wkdpaul
cleaned up

[SkilledRebuilds]

Wow that sleep bug video doing the rounds..

4.0ghz sleep n wakes at 4.2ghz.

 

Sleep is Changing Windows Timing again...

Improving scores after wakeup but its fake as its using 0.85x timing or something... skewing results.

 

[leadeater]

17 minutes ago, LAwLz said:

This does not confirm anything... Even if there is some bug in the scheduler (Microsoft's twitter support just said they would look into it) we still don't know how much of a performance increase it will bring. Again, back when Bulldozer got its fix the performance only increased by 1-2%. Don't expect huge performance gains because it most likely will not happen, and it especially won't bring the Ryzen 7 on-par with the 7700K for gaming.

Well it likely won't increase performance at all, not on workloads that load up cores properly like Cinebench. What it will do is reduce the anomalies and improve minimum results.

 

I mean if we think about it logically it is impossible for it to increase performance, we are talking about a scheduler. Performance of the CPU isn't going to change, certain application performance will improve.

[cj09beira]

2 hours ago, yian88 said:

Stop dreaming and hope threads, ryzen just isnt as good in IPC for gaming and they failed to have a smooth launch because of memory/BIOS issues.

Ryzen wont get better, because x86 cpu's are not gpu-s, they dont have drivers with millions of lines of codes and possibility to optimize drivers for each app/game.

Its either good since day one or it isnt. New bios might help with memory and windows fix with SMT a bit but thats it, the IPC will stay the same, and nothing changes the fact that the silicon from globalfoundries used in zen is complete garbage cant even OC at all.

They really need to make Zen+ release in mid 2018 and fix all the problems + better IPC for games and better silicon for OC.

This is not a optimization issue this is a scheduler issue. Ryzen uses a diferent memory architecture than intel, the problem us that win10 is treating all threads as real cores, that wouldn't be a problem but because of how the l3 cache works windows is making the have to go fetch info to main memory much more often than it would normally. And because main memory is much slower we are seening a performance hit. 

Programers just say give x threads its windows that chooses which cores to give them. 

 

[LAwLz]

9 hours ago, Morgan MLGman said:

Well, considering that with SMT disabled you get up to 20% performance more in some games then it won't be lower than this value.

You have ridiculously high expectations, my naive little friend.

If you expect 20% or higher performance increase then prepare to get disappointed.

 

9 hours ago, Morgan MLGman said:

Well, you're just wrong here so stay within your unrealistic world. If you don't know what you're talking about, this post may just as well be classified as spam.

No Morgan. You're the one who lives in a fantasy world.

 

 

9 hours ago, Space Reptile said:

unless games use more cores/ threads the better IPC will always win

It's not just about IPC either. It's IPC * clock, and Ryzen is behind in both regards.

 

9 hours ago, Space Reptile said:

but in games like BF1 the 77k is pegged when running for max fps while the R7 is at like 40% usage

yet the difference in FPS is less than 10%.

it shows that the R7 has a lot more headroom , but games cant use it

CPU usage % in Windows is not a good indicator of how much headroom you got, nor is it a good indicator of what kind of performance you could expect if a program/scheduler was updated.

 

9 hours ago, Space Reptile said:

no shit Sherlock , unless games use more cores/ threads the better IPC will always win

People in this thread are expecting a minimum of 20% performance increase already. I am just trying to make people lower their expectations.

I am sure that a lot of people who are buying into the scheduler hype will be disappointed when/if an update is released, and then they will go on to talk about the next update that will surely make Ryzen awesome!

 

I mean come on...

First we had a ton of hype about how Ryzen would kill Intel.

Then performance was not anywhere close to what a lot of (dumb) people expected.

So of course they blame motherboard manufacturers for the poor performance.

But what happens when BIOSes were upgraded and it still showed similar performance? They start blaming Windows.

Once Windows is "fixed", I am sure they will go on to blame application developers... It's like it's everyone's fault except AMD's that Ryzen doesn't perform like some people were expecting, and instead of just admitting that they go on to the next thing to wait for that will surely make Ryzen as awesome as they once imagined.

 

9 hours ago, Space Reptile said:

this fix will give you more performance because as I already said , lesser threaded applications get assigned less powerful threads instead of the more powerful cores by accident because 10 cant tell the difference , it WILL improve performance by default , not 70% , not 50% but you can look at something like 10%

The same happened with Bulldozer. Windows assigned two threads to the same module, so they had to share some resources (similar, but not quite like what is supposedly happening right now with Ryzen).

[Space Reptile]

8 minutes ago, LAwLz said:

The same happened with Bulldozer. Windows assigned two threads to the same module, so they had to share some resources (similar, but not quite like what is supposedly happening right now with Ryzen).

you are comparing a Pentium 4 w/ a Core2 here , that's how different Zen is to Dozer , stop comparing the 2

 

[Citadelen]

7 minutes ago, LAwLz said:

-snip-

Performance in gaming wasn't anywhere near what people expected, productivity is great, the point is that gaming is worse than it should be, and this patch should help that ever so slightly.

[LAwLz]

1 minute ago, Citadelen said:

Performance in gaming wasn't anywhere near what people expected, productivity is great, the point is that gaming is worse than it should be, and this patch should help that ever so slightly.

Is it really worse than expected though?

Just from the clock speed alone the Intel chip has more than a 20% lead. Add to that the better IPC and you end up with the 25-30% we are seeing in benchmarks. If we add to that the fact that Ryzen just isn't as good in some areas we could explain the few games where the difference is slightly larger than that.

 

 

12 minutes ago, Space Reptile said:

you are comparing a Pentium 4 w/ a Core2 here , that's how different Zen is to Dozer , stop comparing the 2

Just don't come crying to me when you once again gets disappointed by Ryzen because your expectations are set ridiculously high.

 

Oh who am I kidding, people will just cherry pick benchmarks like crazy regardless of if the supposed patch fixes the alleged issue. Just like how everyone was posting the Joker's benchmarks and ignored every other one.

[Space Reptile]

4 minutes ago, LAwLz said:

Just don't come crying to me when you once again gets disappointed by Ryzen because your expectations are set ridiculously high.

I never expected it to beat a 77k , I never recommended anyone to upgrade to ryzen if they have sky or kaby

heck even broadwell e

 

this is a cpu for sandy and haswell users

[Morgan MLGman]

20 minutes ago, LAwLz said:

You have ridiculously high expectations, my naive little friend.

If you expect 20% or higher performance increase then prepare to get disappointed.

 

No Morgan. You're the one who lives in a fantasy world.

You did not read with understanding, you just read what I wrote.

 

2 hours ago, Morgan MLGman said:

Well, considering that with SMT disabled you get up to 20% performance more in some games then it won't be lower than this value. So it's pretty much: any performance gains from having SMT disabled in specific games will be the lowest value that the scheduler fix should bring for the SMT-on setting.

Some games. That's the keyword. There also are games where turning off SMT lowered performance, those shouldn't be impacted in a meaningful way, but games in which the difference was very noticeable with SMT disabled will benefit at least by the amount of FPS you gained from disabling it. I personally expect it to help even more as power management issues are also what holds performance back in some applications (judging by the fact that the high-performance power plan improves perfomance in some cases)

[Valentyn]

13 minutes ago, LAwLz said:

Is it really worse than expected though?

The only thing worse than expected is gaming. 

We started our Zen speculations that it'll at 'best' match Haswell's IPC.
Instead we have IPC between Haswell and Broadwell.
 

That's fantastic given how far behind AMD was. Since the IPC in Single thread is between H and B, we know it can deliver good performance. We see it really well in production and synthetic tests; in both single, and multi threaded.

There's clearly an issue in gaming, especially on Windows 10. When someone tests a game in Windows 7 and sees up to a 13fps increase, there's clearly something up. ( Although only one person has tested this so far, and we need more published tests )

If some updates brings up the Gaming performance, that's great; whether is 1-5%.

Even though that still puts them slightly under some Haswell chips in gaming.

Then AMD is still competing extremely well on Price, given their performance.

 

Also in response to Joker vids, people also posted ComputerBase a lot, and in many modern games released in 2016 and onwards, the 1800X beats the 7700K; although it still lost to X99 cpus.

 

[LAwLz]

23 minutes ago, Morgan MLGman said:

Some games. That's the keyword.

Such as? I highly doubt we will see a 20% performance increase (or more) in more than one or two games, and chances are those gains won't be from a scheduler update since it's not like a bug like this supposedly is will only affect certain games to that degree.

 

25 minutes ago, Morgan MLGman said:

There also are games where turning off SMT lowered performance

This is the case with Hyperthreading too. I haven't checked it out in recent years, but even with Ivy Bridge you could find programs that performed worse with Hyperthreading on compared to off. That was not a Windows scheduler issue, since the scheduler was already Hyperthreading aware.

 

40 minutes ago, Morgan MLGman said:

I personally expect it to help even more as power management issues are also what holds performance back in some applications (judging by the fact that the high-performance power plan improves perfomance in some cases)

High-performance power plan improves performance on all platforms... It's not a Ryzen specific "issue". That's how it is meant to work.

[flipped_bit]

1 hour ago, Citadelen said:

Performance in gaming wasn't anywhere near what people expected, productivity is great, the point is that gaming is worse than it should be, and this patch should help that ever so slightly.

No one should have expected AMD to make up the huge deficit in IPC in one generation.  Nor should anyone have expected AMD to catch Intel in max clock speeds.  Given both IPC and max clocks have a direct bearing on gaming performance in some games, Ryzen is performing as expected.  If anything, it's performing better than expected.

 

Depending on the benchmark IPC looks to be between Haswell and Broadwell level.  Ryzen is already capable of delivering a high quality gaming experience, and if these software bugs get sorted out then it will be very close to the 6900K in all titles.

 

 

[Space Reptile]

12 minutes ago, LAwLz said:

Such as? I highly doubt we will see a 20% performance increase (or more) in more than one or two games, and chances are those gains won't be from a scheduler update since it's not like a bug like this supposedly is will only affect certain games to that degree.

any game that uses less than 6/8 threads imo , since there is 8 threads that are not real cores a game can be fully assigned  "bad" cores and thus perform worse , as some games have shown , if you turn SMT off and let only the REAL cores do the work games have shown improved performance  

[LAwLz]

3 minutes ago, Space Reptile said:

any game that uses less than 6/8 threads imo , since there is 8 threads that are not real cores a game can be fully assigned  "bad" cores and thus perform worse , as some games have shown , if you turn SMT off and let only the REAL cores do the work games have shown improved performance  

OK

So according to you the vast majority of games will see a ~20% increase in FPS if the scheduler gets patched?

I think you are out of your mind and is setting yourself up for a massive appointment, but we will see.