August 2016 | The Old New Thing

The ship date predictor: Redux

Raymond Chen August 31, 2016 Aug 31, 2016 08/31/16

Last year, I shared the ship date predictor. My colleague who created the chart contacted me last year and told me what happened when he tried to apply the ship date predictor to subsequent projects. He discovered that "the rules for Windows 95 didn't carry over, so my nomination for the Nobel Prize in Project Management was withdrawn." He ...

What is the NTDiskQuotaSidCache.ndx file for?

Raymond Chen August 30, 2016 Aug 30, 2016 08/30/16

A customer was looking for information about the file %LOCALAPPDATA%\Microsoft\Windows NT\DiskQuota\NTDiskQuotaSidCache.ndx. All they could find is this KB article. The NTDiskQuotaSidCache.ndx file is used by the Disk Quota control panel. It's a cache of SIDs and names, to improve ...

Detecting what language or script a run of text is written in, redux

Raymond Chen August 29, 2016 Aug 29, 2016 08/29/16

Some time ago, I discussed the confusion surrounding the question, "How can I detect the language a run of text is in?" because the person asking the question was from an East Asian country, and in that part of the world, scripts and languages line up pretty closely. Chinese uses Hanzi, Korean uses Hangul, Japanese has a few scripts, Thai has ...

Spurious wakes, race conditions, and bogus FIFO claims: A peek behind the curtain of WaitOnAddress

Raymond Chen August 26, 2016 Aug 26, 2016 08/26/16

We spent the past few days looking at the WaitOnAddress function. Today we're going to peek behind the curtain. Reminder: These are undocumented implementation details and are subject to change at any time. The information is presented here for educational purposes. Do not take dependencies on the implementation.¹ Okay, let's ...

Soarin’ over California + Seattle = Wings over Washington

Raymond Chen August 25, 2016 Aug 25, 2016 08/25/16

We already have a giant Ferris wheel. And opening today, right next door to the Great Wheel, we get Wings over Washington, a Washington-themed version of Soarin' over California Around the World, Surprisingly, there has been very little publicity about this new attraction. If anybody goes, let me know what you think. At least it wasn't an ...

Implementing a critical section in terms of WaitOnAddress

Raymond Chen August 25, 2016 Aug 25, 2016 08/25/16

Last time, we built a synchronization barrier out of WaitOnAddress. Today, we'll build a critical section. Remember that this is an exercise just to demonstrate ways of using WaitOnAddress; in real life, you should just use EnterCriticalSection because it has stuff like spin counts and lock convoy resistance. ...

The International Fair Play Committee announces the Rio 2016 Fair Play Awards, but spends most of the time congratulating themselves

Raymond Chen August 24, 2016 Aug 24, 2016 08/24/16

The International Fair Play Committee announced the winners of the Rio 2016 Fair Play Awards, though you'll be hard-pressed to find those winners because the press release spends over 300 words congratulating themselves by listing various officials who gave speeches about the importance of fair play, before finally getting around to naming the...

Implementing a synchronization barrier in terms of WaitOnAddress

Raymond Chen August 24, 2016 Aug 24, 2016 08/24/16

Last time, I promised to reimplement existing synchronization objects in terms of WaitOnAddress. Note that these are academic exercises rather than recommendations, because you should probably just use the existing synchronization objects instead of trying to roll your own. (Also, because the existing synchronization objects are ...

WaitOnAddress lets you create a synchronization object out of any data variable, even a byte

Raymond Chen August 23, 2016 Aug 23, 2016 08/23/16

The WaitOnAddress function is a funny little guy. It lets you create a synchronization object out of 1, 2, 4, or 8 bytes of memory. And you even control the contents of the memory, so the synchronization object costs you nothing! Basically, the WaitOnAddress function waits for the contents of a block of memory to change. ...

Adventures in application compatibility: The bogus memory calculation

Raymond Chen August 22, 2016 Aug 22, 2016 08/22/16

One of my colleagues shared with me one of his application compatibility stories. There was a program that would fail on some computers but not others, and it wasn't clear why. The problem was traced to the size of an internal cache. Now, GlobalMemoryStatus officially returns unsigned values, but if the calling application is not ...

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