Windows 7 On Multicore — How Much Faster?

snydeq writes "InfoWorld's Andrew Binstock tests whether Windows 7's threading advances fulfill the promise of improved performance and energy reduction. He runs Windows XP Professional, Vista Ultimate, and Windows 7 Ultimate against Viewperf and Cinebench benchmarks using a Dell Precision T3500 workstation, the price-performance winner of an earlier roundup of Nehalem-based workstations. 'What might be surprising is that Windows 7's multithreading changes did not deliver more of a performance punch,' Binstock writes of the benchmarks, adding that the principal changes to Windows 7 multithreading consist of increased processor affinity, 'a wholly new mechanism that gets rid of the global locking concept and pushes the management of lock access down to the locked resources,' permitting Windows 7 to scale up to 256 processors without performance penalty, but delivering little performance gains for systems with only a few processors. 'Windows 7 performs several tricks to keep threads running on the same execution pipelines so that the underlying Nehalem processor can turn off transistors on lesser-used or inactive pipelines,' Binstock writes. 'The primary benefit of this feature is reduced energy consumption,' with Windows 7 requiring 17 percent less power to run than Windows XP or Vista."

Comments

Re:Not Really

[timeOday]

It's not surprising because the OS really can't do that much to improve (or mess up) the performance of user-mode code that isn't making many OS calls anyways.

What is surprising is that power consumption could be so significantly reduced. This story could have come out with an entirely different spin if the headline were simply, "Windows 7 Reduces Power Consumption by 17%."

Re:Not Really

[setagllib]

I disagree - user-mode code, whether it's separated into threads or processes, still relies very heavily on kernel scheduling decisions. It may sound simple enough, but if you study the decisions the kernel has to make (such as which thread to wake first, from a set of 8 all waiting on the same semaphore), you can find lots of ways to get it wrong. We now take it for granted because thousands of man-years have been spent on solutions.

Re:Not Really

[SpryGuy]

While actual performance may not be faster, perceived performance almost certianly is. It "feels" snappier, seems to respond better, due to some optimizations in locking and in the graphics subsystem that allows visual feedback in one app to not be blocked or held up by work going on in another app.

Re:Something is wrong with Win7 power management

[ettlz]

I believe fan control in a protected-mode operating system operates in one of the following ways.

• ACPI embedded controller, a separate microprocessor in the chipset that runs its own firmware (typically packaged alongside the BIOS) that monitors the temperature and controls fans in manner orthogonal to the goings-on of the rest of the system.
• System-management mode where, upon detecting some thermal condition, the chipset puts the CPU into a special operating mode that executes a particular piece of BIOS code presumably to emulate the above. In this case, SMM BIOS code is executed. This happens without the knowledge or control of the operating system.
• Protected-mode ACPI control whereby the OS kernel runs the ACPI tables (read from the BIOS on boot) on a virtual machine. These tables include some bytecode to activate the fan once a trip-point is reached. x86 binary found in the BIOS is not invoked here.

The first is clearly the most desirable, as SMM is just plain wrong, and hardware protection should not rely upon the stability of the operating system.

What's happening in your case could be a problem with the EC somehow becoming confused, which is likely either a BIOS or EC firmware bug.

Re:Windows 7 is better than Linux

[jim_v2000]

I always find the Linux vs Windows debate so comical. Windows is a desktop OS trying to be a server, and Linux is a server OS trying to be a desktop.