Inside the Windows Vista Kernel

[iMav]

Inside the Windows Vista Kernel
At a Glance:

* Thread priority and scheduling
* File-based symbolic links
* Canceling I/O operations

This is the first part of a series on what's new in the Windows Vista kernel. In this issue, We will look at changes in the areas of processes and threads, and in I/O. Future installments will cover memory management, startup and shutdown, reliability and recovery, and security.

The scope of this article comprises changes to the Windows Vista™ kernel only, specifically Ntoskrnl.exe and its closely associated components. Please remember that there are many other significant changes in Windows Vista that fall outside the kernel proper and therefore won't be covered. This includes improvements to the shell (such as integrated desktop search), networking (like the new IPv6 stack and two-way firewall), and the next-generation graphics model (such as Aero™ Glass, Windows® Presentation Foundation, the Desktop Window Manager, and the new graphics driver model). Also not covered are the new Windows User-Mode and Kernel-Mode Driver Frameworks (UMDF and KMDF) since these are back-level installable on earlier versions of Windows.

CPU Cycle Counting

Windows Vista includes a number of enhancements in the area of processes and threads that include use of the CPU cycle counter for fairer CPU allocation and the new Multimedia Class Scheduler Service (MMCSS) that helps media applications deliver glitch-free playback.

All versions of Windows NT® up to and including Windows Vista program an interval-timer interrupt routine to execute approximately every 10 or 15 ms (milliseconds), depending on the hardware platform. The routine looks at what thread it interrupted and updates the thread's CPU usage statistics as if that thread had run for the entire interval, while in reality the thread might have started executing just before the interval's end. Further, the thread might have been technically assigned the CPU, but didn't get a chance to run because hardware and software interrupt routines executed instead.

While clock-based time accounting might be OK for diagnostic tools that report thread and process CPU usage, use of that method by the thread scheduler can cause unfair CPU allocation. By default, on client versions of Windows threads are permitted to run up to 2 clock ticks (6 if in the foreground). However, the thread might get virtually no time on the CPU or up to 6 ticks (18 if in the foreground), depending on its behavior and other activity on the system.

A lot more with images go Here

[Josan]

Haah Haaah!!!!!!!!!

[iMav]

whats that supposed to mean