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Windows 7's dirty secrets revealed

Hidden work arounds and complex dependencies


How about reliability? This was fascinating. Microsoft observed that 15 per cent of all user-mode crashes and 30 per cent of shutdown crashes were caused by heap corruption: applications that try to access freed memory, or memory beyond what is allocated. Its solution was a feature called the Fault Tolerant Heap (FTH).

If an application crashes a few times, Windows will automatically apply a shim that intercepts its memory operations. FTH will over-allocate memory, and keep a copy of freed memory so that attempts to re-read it will succeed. The user gets better reliability at the expense of performance, which suffers by up to 15 per cent or so, while buggy applications work better than you would expect.

Developers expressed some concern. Were their mistakes being disguised so that they would remain unfixed? It is a risk, though if Windows detects a debugger the feature turns itself off. You can also disable FTH, though not on a per-process basis.

UAC won't protect you from malware

Russinovich also spoke about the contentious User Account Control (UAC), which prompts the user to approve actions that should require administrative rights. "UAC is not an anti-malware solution," he said. "If you think you are safe from malware because you are in one of those prompting modes, you're wrong. If malware gets on your box, and you are admin, you must assume that malware will gain admin rights."

Proving the point, he showed how a genuine, signed Microsoft executable might load a malicious process, invisible to the user. So what is the point of UAC? "It is about one thing, which is about getting you guys to write your code so that it runs well as standard user."

There was more: how the .VHD virtual hard drive format might become a standard container to replace ZIP, and the advantages of booting from a VHD. Also, how Windows 7 attempts to reduce power consumption with tricks like putting idle processor cores to sleep in a smarter fashion than earlier versions of Windows. Did you know that running powercfg /energy from an administrative command prompt generates an energy efficiency report for your PC?

Russinovich was full of such surprises. Positively, his talk shows the effort Microsoft is putting into rescuing Windows from its muddled legacy and buggy applications; negatively, he reveals just how many odd workarounds exist under the surface. ®

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