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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