Archives for posts with tag: Kernel

Inside Windows 7: Recovering Windows from System Degradation and Boot Failures [Inside Windows 7: Recovering Windows from System Degradation and Boot Failures]

November 30, 09 //
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Windows 7 is capable of certain levels of self-repair, as you’ve learned. One of the new capabilities in Windows is its ability to recover from serious failures that can impact the OS’s ability to boot. How does Windows 7 handle these errors? Can you boot Windows 7 into Safe Mode or to an earlier functional state when something really bad happens? Yes. You can, depending on the nature of the problem. How?

Stephan Doll, Pavan Kasturi, Desmond Lee and Baskar Sridharan make up most of the team that has enabled Windows 7 to be the most recoverable version of Windows to date. By ensuring that every Windows 7 machine has the ability to automatically diagnose and recover from most boot failures with little or no interaction from the user, this team’s work promises to greatly reduce—or even eliminate—the impact of a serious issue that would otherwise cause significant pain for Windows 7 users.

Tune in.

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Mark Russinovich: Inside Windows 7 Redux

October 22, 09 //
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Windows 7 is here, available to all for purchase and ships today with new PCs! To celebrate this momentous occasion for Windows and Microsoft, Technical Fellow Mark Russinovich joins me in a discussion that extends the great conversation we had last year on Windows 7 internals. In his previous C9 interview, Mark told us about many of the new additions to the Windows kernel which enable Windows 7 (and Windows Server R2) to scale to large numbers of processors. Well, removing the kernel dispatcher lock is not all that the great Arun Kishan did. He also developed a new scheduling mechanism known as Distributed Fair Share Scheduling (DFSS). Mark describes what this is and how it works.

We also discuss NUMA, non-uniform memory access, (and Mark explains NUMA to us while showing a demo or two on a 256 processor machine!)

Moving on to Windows memory management, the domain of the great engineer Landy Wang, Mark discusses the new additions to the Windows Memory Manager and explains why they matter to those of us who spend all of our time and in user mode.

Learn about all of this and much more as Mark digs into the insides of Windows 7, way deep down in the system (the culmative effects of which help to make Windows 7 Microsoft’s most reliable, scalable and efficient general purpose operating system to date). As usual, Mark explains very complex mechanisms and concepts in a readily understandable way. This is a very conversational piece and we cover a lot of ground in a relatively short period of time. We also learn exactly why Mark is so passionate about operating systems and what the spark was that set off his passion and curiosity of how things work internally.

Mark will be presenting at PDC09 in the Technical Leaders track and the free Windows 7 Developer Boot Camp. His talks will be very deep and will explore all aspects of the new, improved Windows 7 kernel. I highly recommend that you attend both of these talks if you are going to PDC (you’re going, right?!).

Check out the Windows area on 9 for more great Windows 7 content, all rolled up into a nice experience!

Enjoy!

Note: Check out all the 9 Guys Mark has. :) Also, you should subscribe to his incredible blog.

Silviu Calinoiu: Inside Windows 7 – Fault Tolerant Heap

August 25, 09 //
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The Fault Tolerant Heap (FTH) is a subsystem of Windows 7 responsible for monitoring application crashes and autonomously applying mitigations to prevent future crashes on a per application basis. For the vast majority of users, FTH will function with no need for intervention or change on their part.

Principal Development Lead and rock star developer Silviu Calinoiu is the mastermind behind FTH. Here, we go deep into how FTH works and why it’s designed the way it is.

The Fault Tolerant Heap is another example of the low level efficiency built into the system: FTH automatically corrects memory faults that cause applications to crash which has the pleasant side effect of preventing future crashes. How does FTH work, exactly? What types of memory problems does it address, specifically? How do developers monitor FTH events and can they override FTH’s behavior? What does this all mean to the average user?

FTH, as an autonomous monitoring and correction system, represents a step in the right direction for the evolution of a more homeostatic general purpose operating system. Simply, Windows is getting smarter in the sense that it’s increasingly becoming better at self-regulation and self-healing. Yes, there’s a very long way to go, but we’re making real progress.

You will continue to learn about recoverability in Windows over the coming months here on C9.  

Tune in.

Arun Kishan: Inside Windows 7 – Farewell to the Windows Kernel Dispatcher Lock [Arun Kishan: Inside Windows 7 - Farewell to the Windows Kernel Dispatcher Lock]

August 6, 09 //
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You’ve learned about many of the new features of the latest version of the Windows kernel in the Mark Russinovich Inside Windows 7 conversation here on Channel 9. One of Mark’s favorite kernel innovations is the way the Windows 7 kernel manages scheduling of threads and the underlying synchronization primitives that embody kernel thread management.

Prior to Windows 7 (and therefore Windows Server 2008 R2) the Windows kernel dispatcher employed a single lock, the dispatcher lock, which worked well for a relatively small numbers of processors (like 64). However, now that we find ourselves in the midst of the ManyCore era, well, 64 processors aren’t that many… A new strategy was required to scale Windows to large numbers of processors since a single lock is limited in capability, by design: The masterful David Cutler, one of the world’s greatest software engineers, wrote the NT scheduler in a time when the notion of affordable 256-processor machines was more science fiction than probable. 

As we learned in the Mark Russinovich video, Windows 7 can now scale to 256 processors thanks to the great engineering of Arun Kishan, a kernel architect you’ve met on C9 back in the Vista days. In order to promote further scalability of the NT kernel, Arun completely eliminated the dispatcher lock and replaced it with a much finer grained set of synchronization primitives. Gone are the days of contention for a single spinlock. How did Arun pull this off, exactly, you ask? Who is this genius? Well, tune in. Lots of answers await…

Arun’s work directly benefits the overall performance of Windows running on many processors and means, simply, Windows can now really scale. Thank you, Arun!

 

Spinlocks are synchronization primitives that cause a processor to busy-wait until the state of the lock’s memory location changes.

 
As the name implies, the dispatcher lock is the fundamental lock associated with the kernel dispatcher, or the scheduler.

 

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