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DPCs and ISRs run at an elevated interrupt request level, or IRQL (DISPATCH_LEVEL and device IRQL, respectively. A driver that spends too much time in its DPCs and ISRs prevents the system from servicing threads, which degrades overall system performance. The Microsoft Windows Vista Logo Program requires that:
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An ISR does not run longer than 25 microseconds.
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DPC does not run longer than 100 microseconds.
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You can measure the time that kernel-mode drivers spend in DPCs and ISRs by using a new feature of Tracelog, a command-line tool provided with the Windows Driver Kit (WDK) that manages software tracing sessions. The DPC/ISR feature of Tracelog captures the activity of all drivers running in the kernel during the trace, even drivers that are not instrumented for tracing.
Microsoft Windows XP SP2 and later versions are instrumented for DPC/ISR tracing. To actually trace DPC/ISR activity, however, you need the version of Tracelog provided in the WDK. This tool is installed in the %winddk%\tools\tracing folder.
What should you do in the drivers you are developing?
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Use Tracelog with the -dpcisr parameter to find out how much time your driver spends in its DPC and ISR routines.
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Optimize your driver's DPC and ISR routines to run as quickly as possible.
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Happy tracing!
—Annie Pearson for the WHDC team
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WHDC After Dark. This week, not all the After Dark fun will cause you to say "Yikes!" (Though I warned you previously not to click the bonsai kitty link, it appears many chose to ignore my warning.)
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SNAil-based Data Transfer Protocol: The fastest last-mile data transfer technology available today, as demonstrated in this paper published in the Annals of Irreproducible Research.
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Putting Windows XP in Your Car: Channel 9 features J. P. Stewart, a member of the CarPC Club at Microsoft, showing how he tore apart his car, put Windows XP, Wi-Fi, GPS, and other things into his car, and then put it all back together. (Personal confessions of a Luddite: In my family, we retain old-fashioned ways: a cigarette-lighter extension for the person in the backseat with a laptop, plus analog gauges on the dashboard.)
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Windows Vista - Design and Development News
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TMM enables the automatic detection and setup of displays as they are attached and removed. This new white paper documents the behavior and operation of TMM as well as the related requirements for the Windows Vista Logo Program.
Notes from the Windows developers on the new features and capabilities in Windows Vista that improve memory management, focusing on dynamic system address space, enhanced NUMA and large system/page support, advanced video model support, I/O and section access, and robustness and diagnosability.
Changes to the format and organization of kernel-mode and user-mode header files (.h files) in the WDK, together with best practices for driver developers who create drivers for Windows Vista.
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Windows Vista Logo Program
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You can now download and review Windows Vista Logo Program System and Device Requirements, Version 3.0, Revision Draft 0.6. This draft applies only to client systems and device products that will run on a Windows Vista operating system. This document does not supersede earlier releases for devices or systems that run earlier versions of Windows such as Windows XP or Microsoft Windows Server 2003.
Feedback is being requested on the 0.6 draft. Submit feedback and any questions by e-mail to hwlogo@microsoft.com.
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Kits and Tools
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The SDK August 2005 Update download contains the tools required to build cutting-edge, media-rich, interactive applications. It includes run times, headers and libraries, samples, documentation, utilities, and support for C++, and Managed Code development.
This same download Web site contains the Microsoft DirectX 9.0c symbol files and the end-user redistributable, which includes an updated DirectX for Managed Code and D3DX.
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Event Tracing References
For more information about event tracing and optimizing DPC and ISR routines:
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Edition for
