AMD: There’s Nothing Wrong with the Windows 10 Scheduler

Posted on March 14, 2017 by Paul Thurrott in Hardware, Windows 10 with 21 Comments

Earlier this month, AMD launched its Ryzen microprocessors to near-universal acclaim. But when a tech blog claimed that Ryzen didn’t function properly on Windows 10, AMD investigated. And it has now debunked that as myth.

I haven’t really covered Ryzen properly, but I’m intrigued by AMD’s return to the sweet sport of the market: No, Ryzen can’t match the performance of the best Intel microprocessors, but it appears to deliver a vastly superior bang for the buck, with much lower prices. In some cases, literally half the price of a comparable Intel chip.

In any event, right after the initial glow from the positive reviews subsided, a report in Wccftechclaimed that a bug in the Windows 10 scheduler was responsible for Ryzen performance issues on that platform.

“Windows 10′ scheduler correctly identifies Intel’s hyper-threads as lesser performing than principal core threads and schedules tasks in a way that takes advantage of the additional throughput without negatively impacting performance,” the site reported. “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.”

This week, however, AMD chimed in on this issue. And it says that there is nothing wrong with the Windows 10 scheduler.

“We have investigated reports alleging incorrect thread scheduling on the AMD Ryzen processor,” an AMD statement notes. “Based on our findings, AMD believes that the Windows 10 thread scheduler is operating properly for ‘Zen’ [Ryzen’s processor architecture], and we do not presently believe there is an issue with the scheduler adversely utilizing the logical and physical configurations of the architecture.”

AMD also compared thread scheduling between Windows 7 and Windows 10 on Ryzen and has found them to be substantially similar.

“We do not believe there is an issue with scheduling differences between the two versions of Windows,” AMD wrote. “Any differences in performance can be more likely attributed to software architecture differences between these OSes.”

AMD adds that version of the Sysinternals Coreinfo utility used by Wccftech is out-of-date, and that the latest version of this utility will give the proper results.

In other words, nothing to see here.

 

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Comments (23)

23 responses to “AMD: There’s Nothing Wrong with the Windows 10 Scheduler”

  1. Subhadip Sen

    PC Perspective investigated this issue in great detail - https://www.pcper.com/reviews/Processors/AMD-Ryzen-and-Windows-10-Scheduler-No-Silver-Bullet

    Windows 10 works just fine. This is a simple matter of Zen being a brand new futuristic architecture, while older games are developed and optimized for Intel. Give it a year or two, this will be a non-issue.

    I can't wait for Ryzen mobile this fall. Ryzen actually has better efficiency than Intel, especially at idle, so this could bring ARM-like battery life to x86. And AMD's embedded GPUs have always been superior. I won't be surprised if Surface Book 2 is delayed till Fall 2017 for Ryzen. Scorpio and Surface Book with cutting-edge AMD tech - who would have thought?

    PS: Intel has never made such a transparent blog spot.

    • Polycrastinator

      In reply to Subhadip Sen:

      I think you're placing too much hope in AMD here. The single threaded performance is still behind Intel, and where you're reducing down to only a couple of cores such as in laptops, I think they'll still be ahead. AMD really has something here for multi threaded workloads, and it's great to see them competitive again, but there's still a lot to prove outside of the high end desktop market. Maybe they'll pull a rabbit out of the hat, but there's a reason they've started with this chip design, and I expect that's because it's the environment where they're most competitive.

    • Darmok N Jalad

      In reply to Subhadip Sen:

      I haven't checked every review, but I hadn't seen much discussion on power consumption. I usually turn to Anandtech for the most complete review, but they didn't cover it. Power consumption certainly is one more way to compare to Intel, especially when looking for mobile solutions that are far more popular now.

    • Luka Pribanić

      In reply to Subhadip Sen:

      And this Xbox + Scorpio + maybe Surface Book is yet another reason why AMD probably said everything is OK with W10. If they want Microsoft to finally shatter the WinTel alliance, they've got to be good with them, tell everyone that W10 is perfect, and MS will buy lots of chips, optimize for them (AMD), and so on. Looking at what Qualcomm did, seems to work, took them 5-6 years but look what happened. If AMD ca do similar, with Qualcomm tearing one end, and AMD attacking the other, Intel sholud be way less a monopoly. And no more Wintel. Competition is good, even if sometimes you have to swallow a bad pill once in a while, for the partnership's sake... No worries though, if it goes this way, and news are correct, MS will take a good care of their "new" partner, and will fix what needs fixing

  2. awright18

    Not sure they would admit to poor performing highly sought after brand new processors. Blaming their partners really wouldn't make sense, and in any case, software from either AMD or Microsoft will fix the issues. So I think they were just carefully crafting their words to put out a potential fire. Their statement helps everyone involved consumers, AMD, and Microsoft, regardless of the truth of the matter as any real issues will be resolved in a timely matter.

  3. Waethorn

    How can it be a "virtual thread" when Windows treats threads equally? I don't see his argument. He states: "Windows 10′s [sic] scheduler correctly identifies Intel’s hyper-threads as lesser performing than principal core threads". He's incorrect. Not only that, he's saying that AMD's chips perform the same as Intel's. His argument is false.

    • jimchamplin

      In reply to Waethorn:

      The cores can't dedicate as much to the second thread as to the primary one, so the scheduler won't assign high-priority tasks to those virtual threads. If you're say, transcoding video, the threads pertinent to that will run on the physical CPU cores while the UI code for the status bar will be on a virtual core that's surfaced by SMT.

      • Waethorn

        In reply to jimchamplin:

        Right. That's the cores doing that. The scheduler should be letting the cores do that by themselves. From Microsoft's own [albeit limited] documentation, they're all "virtualized" cores when you're talking about SMT.

        • CaedenV

          In reply to Waethorn:

          This is exactly the problem; the task scheduler is treating all cores equally, and thus not weighting to the primary cores first as it does on an Intel HT setup. It is not that win7 runs particularly better, or that win10 does not work, it is merely that AMD forgot to involve software partners during the development process so Windows and other software simply does not run optimally. Nothing is broken, and that is why AMD is claiming that nothing is wrong... but nothing is optimized either, so we should expect to see a nice little performance bump over the next few months as drivers, OSs, software, firmware, and microcode all get updated.

  4. Daekar

    I hope for AMD's success. I would love to see them kick Intel down the road and master ARM-level efficiency out of x86-64 architectures.

  5. kjb434

    Noticed in the standard comments someone linked to PC Perspectives podcast and thorough write up on this issue. They came to the same conclusion as AMD. They made some guesses at what the cause may be for any perceived performance issue, but admit further testing would be needed.


    Ultimately, Ryzen is still an amazing value compared to equivalent Intel processors. I'm considering using Ryzen for my next build, but waiting for more testing and to see if Intel will respond.

  6. Martin Pelletier

    Weird, I saw a report (in french news) that Microsoft is working on a patch for Ryzen for Windows 10. Saw that on the News App yesterday.


    http://www.generation-nt.com/amd-ryzen-processeurs-microsoft-windows-10-problemes-support-smt-simultaneous-multi-threading-patchs-correctifs-actualite-1940439.html


    It will be better with new games this year. I will buy an 1800x when I can.

  7. gamersglory

    Zen's main problem is that it's a completely new Architecture built from the ground up so windows support is not where it is for Kaby Lake as Kaby Lake is the 7th generation of the Core I architecture which has had time to iron out bugs and get windows and drivers optimized

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