In the xperfview screenshot below you can see the three diamonds in the Generic Events graph which represent movement of the mouse wheel, and on the CPU usage graph you can see the burst of CPU activity that was triggered. Rich ETW traces with input data, timer frequency, battery information, optional power draw, and more are available by using UIforETW to record traces. I turned on my ETW input user-provider (yes, it’s a key logger) so that I could see keyboard and mouse events and then recorded a trace.

But on the initial roll of the mouse wheel on a new image there is a delay of about a second before the first image is displayed. And indeed, once I’ve started zooming in on an image the frame rate is excellent – it keeps up with my mouse wheel. The image is already decoded so it should be fast. Zooming in for a closer look on an image is a pretty basic operation. It is not the worst hang I have seen – those when tagging photos or rapidly advancing through photos are much longer – but it is the simplest, and I suspect it is representative of the architectural problems that make WLPG not as responsive as it should be. I eventually found a simple scenario that let me reliably produce a short hang, and this is what I analyzed. I have a four-core/eight-thread Sandybridge machine with 8 GB of RAM and there is, I believe, no reason for significant delays as I skim through my photos. I frequently notice small hangs (from one to five seconds) when tagging photos or browsing through photos with WLPG. If Microsoft wants Windows to be seen as fluid and fun, like other OSes then it needs to take stuff like this seriously and make sure that avoidable performance problems don’t ruin an otherwise excellent product.

It is possible to work around this, and double the performance of WLPG, but it’s a tricky operation. The net result is that if you try using WLPG on a laptop without an SSD you will get poor performance and poor battery life. My sad conclusion is that it appears that WLPG does a lot of extraneous I/O when zooming images, then busy waits for the results. But I have long been annoyed by its inconsistent performance, and today I investigated. I use Windows Live Photo Gallery (WLPG) because it has powerful features for tagging my photos and sorting through them.

Windows live photo gallery errors