Microsoft Highlights Changes to the Windows Kernel

By Peter Galli  |  Posted 2007-05-16 Print this article Print

At WinHEC, Microsoft technical fellow Mark Russinovich discussed, among other things, how uniprocessor kernel variants were now gone from Windows Server 2008, which reduces the need for downtime.

LAS VEGAS—Attendees at Microsofts Windows Hardware Engineering Conference here got an in-depth and deeply technical keynote outlining the changes to the Windows kernel and other key areas, and how partners can take advantage of these.

In his presentation on May 16, Mark Russinovich, a technical fellow in Microsofts platform and services division and the third keynoter of the day, talked about how uniprocessor kernel variants were now gone from Windows Server 2008, which reduces the need for downtime by supporting hardware configuration changes without the need to reboot the system.
The new server product, which is the basis for Microsofts new virtualization offering, also introduced a new common infrastructure called WHEA (Windows Hardware Error Architecture).
On the time accounting front, Russinovitch said that Windows previously accounted for CPU time based on the interval clock timer and that thread quantum expiration was not always fair. Read more here about why Longhorn falls short. "Windows Server 2008 now reads the Time Stamp Counter at the context switch, which allows for more accurate quantum reporting," he said. Other infrastructure changes include an enhanced thread pool mechanism, new synchronization APIs, private namespaces and hard resource quotas. "SMB is the original Windows remote file system protocol, but it could not adapt to the new NTFS features and was not designed for todays large data sizes. As such, SMB2 has been introduced in Windows Server 2008," Russinovitch said. The server product also defers I/O completion until the thread pulls the I/O off the completion port, which avoids the context switch and improves the performance with no change to the applications, he said. To read more about the first public beta for Windows Server 2008, click here. Windows Server 2008 also introduces I/O prioritization, based on the priority of the issuing thread or the explicitly set I/O priority. "Also, in 32-bit Windows Server 2008, virtual memory is assigned as needed, with kernel page tables allocated on demand instead of at boot time. Kernel stack usage is also reduced through stack jumping. This all supports more users on terminal services," he said. The product also brings memory manager performance improvements, with fewer and larger disk reads for page faults and system cache readahead. NUMA enhancements include more memory allocations being NUMA aware and now the I/O system directs interrupt completion to the node that initiated I/O. The ideal node is used more effectively for process memory allocations and the new NUMA APIs allow applications to specify the preferred node number for memory applications and file mapping, Russinovitch said. Read more here about why Microsoft cut core features from Viridian. With regard to startup and shutdown enhancements, there is now parallel session creation in Windows Server 2008 rather than serial session creation, which was how it was done in previous versions of the product, he said. Windows Server 2008 also has a clean service shutdown, which allows the system more time to shut down. Services can now request a pre-shutdown notification and, after these services stop, the system performs Windows XP-like shutdown, he said. "This is also the first server system that is completely bug free," Russinovitch joked, adding that it was the third-party applications that could cause it to crash. But the new product is better at handling process crashes, with unhandled exceptions sending a message to the Windows Error Reporting service and all process crashes now getting recorded, he said. "In summary, there are lots of exciting kernel changes for performance, scalabilty, reliability and security," he said. Check out eWEEK.coms for Microsoft and Windows news, views and analysis.
Peter Galli has been a financial/technology reporter for 12 years at leading publications in South Africa, the UK and the US. He has been Investment Editor of South Africa's Business Day Newspaper, the sister publication of the Financial Times of London.

He was also Group Financial Communications Manager for First National Bank, the second largest banking group in South Africa before moving on to become Executive News Editor of Business Report, the largest daily financial newspaper in South Africa, owned by the global Independent Newspapers group.

He was responsible for a national reporting team of 20 based in four bureaus. He also edited and contributed to its weekly technology page, and launched a financial and technology radio service supplying daily news bulletins to the national broadcaster, the South African Broadcasting Corporation, which were then distributed to some 50 radio stations across the country.

He was then transferred to San Francisco as Business Report's U.S. Correspondent to cover Silicon Valley, trade and finance between the US, Europe and emerging markets like South Africa. After serving that role for more than two years, he joined eWeek as a Senior Editor, covering software platforms in August 2000.

He has comprehensively covered Microsoft and its Windows and .Net platforms, as well as the many legal challenges it has faced. He has also focused on Sun Microsystems and its Solaris operating environment, Java and Unix offerings. He covers developments in the open source community, particularly around the Linux kernel and the effects it will have on the enterprise.

He has written extensively about new products for the Linux and Unix platforms, the development of open standards and critically looked at the potential Linux has to offer an alternative operating system and platform to Windows, .Net and Unix-based solutions like Solaris.

His interviews with senior industry executives include Microsoft CEO Steve Ballmer, Linus Torvalds, the original developer of the Linux operating system, Sun CEO Scot McNealy, and Bill Zeitler, a senior vice president at IBM.

For numerous examples of his writing you can search under his name at the eWEEK Website at


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