.NET Application very slow after long period of inactivity

Question

I'm not sure if the question title is the best one but it was the best one I could come up with...

I have this .NET (C#) applications which starts up with Windows and remains opened until the computer is turned off. The app stays on the tray and I open it by clicking the tray icon and close it the same way.

The app is not slow at first, it works normally, no problems there. But after long periods of inactivity of itself, it gets very slow when showing it again for the first time in a long period. Know what I mean.

For instance, I could not use/open (click the tray icon) for a few days and between those days I opened and closed and used lots of other apps, heavy apps too and I probably hibernated and resumed the computer a few times and when I needed to open my app again, it was slow. After a few minutes of using it, it goes back to normal and works fine.

I believe this has something to with memory management and the system probably frees up most of my app's memory so other programs can use it more efficiently. And maybe .NET memory management as something to do with it...

Whatever the reason, is there anything I can do to optimize my app regarding that issue?

Answer 1

This is almost certainly due to memory being paged out to disk.

When you cease using your application and other applications or tasks start exerting memory pressure, pages of memory from your app can be written out to disk. When you try to use your application again, all this data must then be read in causing the stalls that you see.

Unfortunately, there is no good solution - if you run as administrator or have the SeLockMemoryPrivilege, you can lock parts of your application into physical memory. You can try "touching" pages periodically to keep them in physical memory. Unfortunately, both these options will cause your application to interact badly with other applications on the system - your memory is getting paged out because the physical memory is needed for something else. You can attempt to lower your overall memory footprint, but you will still run into this issue in some cases. There are options for tweaking your working set size, but the OS is free to ignore those, and will in many cases.

Answer 2

You can use the .NET memory profiler to get a good idea of what your application is doing with memory over time. You can check if anything is building up where you don't expect it to (collections, lists, etc.) and causing your memory footprint to grow.

Answer 3

Have you tried double-clicking in Process Explorer on your running app and observe it for leaks? Is it CPU utilization, UI leak, memory leak, recurrent I/O?

Answer 4

如果问题确实是由于长时间不活动而导致程序被分页，您是否尝试设置“保持活动”计时器，每隔几分钟触发一次，这基本上使应用程序处于寻呼系统的状态有没有看到它闲置？

Answer 5

I reckon that this behavior is normal in Windows. Windows will serve the application that is need it most, ie, the application that is currently in used. Thus, if an application is minimized or not active for pro-long duration, like the case specified above, it will be the best candidate for Windows to page the application memory and make available memory to active application. Windows will restore the application memory when it get active from paging memory (hard disk), thus this explain why it is slow.

This might be not the best answer, but if I were you, I will experiment by increasing the base priority of the application. This can be done by using Thread object in .NET framework.

Thanks.

Answer 6

This isn't a root cause answer or solution, but if Michael is right and there's nothing you can really do about it, then you might just want to consider visually informing the user that your application is active with a progress bar or nifty progress circle.

It won't speed up your program, but it may ease the minds of your users just a little bit.