Vista PCs: the hardware resources they are so hungry for

Cross-tabular analysis. It’s one of those nerdy-sounding terms that statisticians like to use when expounding upon their latest data-mining gems. It’s also the lifeblood of the Windows Sentinel project. We use cross-tabular analysis to extract all sorts of interesting statistics from the exo.repository, including how a platform shift can directly affect workload composition.

[ Add your Windows systems to the exo.performance community, plus monitor how they specifically perform, with InfoWorld’s Windows Sentinel tool. ]

For example, did you know that Vista-based PCs are working harder than ever? Aside from the obvious fact that they run slower than they did under Windows XP (in many cases, by 40 percent or more), there are some fascinating changes going on under the hood. If you compare the typical workload of a Windows-based system, breaking it down by per-process thread count and CPU utilization, you see that a Windows Vista PC is using roughly 21 percent more CPU cycles per thread than a comparably configured Windows XP PC. This is in addition to the fact that Vista is spinning almost twice as many execution threads (something we discovered in our recent cross-generational analysis of Windows/Office).

Translation: Not only is Vista “fatter” than XP, it’s also more demanding at a very fundamental level. Hence the need for beefier client hardware with lots of cores.

The above tidbit is something we pulled from the exo.repository using that nerdy, cross-tabular analysis I mentioned earlier. Basically, we extracted the process list for each system in the repository (about 1800 at last count), then compared the total CPU time for all running processes with the thread count for same, factoring in the number of physical/logical CPUs. The resulting compound index – the Thread Utilization Index (TUI) – gave us a handy, single-number ratio that describes how a given workload is behaving at a system-wide level. And when we compared the average TUI for XP and Vista-based systems, we saw a 21 percent spike in the latter.

The great thing about compound indices like TUI is that they’re dynamic: We’ve adapted the algorithm that generates the index to compensate for factors like multiple cores and hyper-threading — things that can directly affect workload behavior/scalability. By abstracting the data from the platform particulars, we make it possible to compare seemingly disparate systems — for example, a quad-core uber-workstation and an aging Pentium M notebook — because the indices acknowledge the context in which they are generated.

Another good example is the Peak Memory Pressure Index. As we analyze the index’s four contributing factors — the Committed Bytes, Pages Input/Sec and Percent Page File Utilization performance counters, as well as the duration of the peak event — we weight each and then evaluate them against the PC’s physical memory capacity. This, in turn, allows us to make those difficult heterogeneous comparisons — for example, the aforementioned Pentium M notebook with 512MB of RAM and the uber-workstation with 8GB. The raw data says that the latter is running a much larger workload, in terms of RAM consumption, than the former. However, in practical terms, both may be comparably burdened in terms of how their respective workloads affect the available physical hardware: Available RAM; paging activity; and so on.

Again, it’s our ability to abstract the data from the hardware that allows us to glean all of these interesting tidbits. It’s also how we can say with confidence that Vista-based PCs are experiencing roughly 30 percent higher memory pressure, across the board, than their XP brethren.

No question: Vista is considerably “fatter” and more demanding than XP. But you don’t need lots of fancy abstract statistics to tell you that. Just boot the thing … and wait … and wait … and wait …