How to solve a very sluggish Windows 10 UI

Some time ago I wrote Windows Perfmon: The Top Ten Counters at my old blog. The article is a quick introduction to using Perfmon to determine where hardware bottlenecks are: processor, memory, disk, or network (and secondarily, to determine current operational loads on these resources). I can't emphasize this step enough: first make sure you know which hardware resource is overused. Then go hunting the resource hog.

Once you've determined which resource is overused, you have two choices: add more of that resource (get a faster CPU, add memory, get a faster disk or NIC) ... or track down the top users of that resource, and either kill them or take steps to make them less piggish.

The easiest way to track down top resource hogs is with Process Explorer. Be sure to run it from an account with Admin privs. Here's a quick-and-dirty list of things to look for:

• For memory bottlenecks (the most common bottleneck), use the Working Set, Virtual Size, and Private Bytes History columns from the Process Memory tab. Sort the columns one by one, descending (largest values at top of column). Of these, Working Set is usually the most valuable.
• For CPU bottlenecks, obviously you want the CPU Usage column. CPU History is also handy. These are on the Process Performance tab. Again sort descending. This value tends to jump around a lot more than memory usage values do, so don't make snap judgments. Watch it awhile to see if your prime suspect stays at the top for more than a few seconds.
• For disk bottlenecks (which are often actually memory bottlenecks as the system is forced to page stuff from disk far too often) you don't really have great choices, because Windows doesn't have per-process disk I/O perfmon counters. However you can look at total I/O per process (which includes disk, network, and device I/O) you can use the I/O Read Bytes and I/O Write Bytes counters as a rough estimation. These are on the Process Performance tab.
• Network bottlenecks are unlikely to be your issue, but since per-process network counters are lumped into I/O, you can get a rough idea in the same way I described above for disk bottlenecks. It's up to you to determine whether the I/Os you see in these columns are more likely to be disk or network I/Os. If you were on Vista/2008/7 you'd get a little help here from the Windows Performance Tools which I discuss on my newer blog.

Good luck!

The very first thing to do (always) is to go Event Viewer and to see the recent events. Some may give you a hint of what takes so much resources. For example, it can be a Windows Update which checked for new updates, or Outlook which started to rebuild or rescan something, or Windows itself which indexed new files or whatever else. (Note: it is obviously NOT Windows indexation, since it happens only when the PC is idle).

Then you can try Resource Monitor. To run it from Task Manager, open Performance tab, then click on Resource Monitor button at the bottom. This tool will give you an overview of how CPU, disk, network and memory are used, and may help to track down "instant" processes which are difficult/impossible to see in Task Manager.

Finally, check Task Scheduler. It may give you a hint about a task which took too much resources.