CODEWITHSUNDEEP
windowsqtcompilationmingwcompiler-optimization
Momergil
Momergil

Reputation: 2281

MinGW compiling excessively slow

Since some years ago I started using Qt in both Windows 7 as well as in Linux Ubuntu and it would always compile fast with MinGW being used for Windows. But in the last couple of years or so, maybe thanks to updates in the version of both Qt and MinGW, I started detecting a slow down in the compiling speed inside Windows. I did some research trying to find why MinGW had started to become so slow compared to Linux (it wasn't before!) and everything people told me was that MinGW was slower in Windows and that it would be better, if possible, to just use Linux.

Since I wanted to continue my project, I followed the suggestion and since I've being using Linux with relatively no problems. The situation now is that I must go back to Windows (now updated to Windows 10) to make visual corrections for this OS and I need to once again work with MinGW having to face the same problem as before.

But for some reason it seems that the slowness of MinGW became even worse! While before I at least was able to compile the app in around 4 minutes, now the last time I tried it took 38 minutes before I gave up and went to sleep - and this is for a project that takes only 1:03 minute to be compiled in Linux [under the same compile configuration]!

Well I'm still aware about the slowness of MinGW, but as a quick research around this problem on the web reveals, that is just too slow: all backtesting one can find in other threads here on SO reveals at best 2x-3x more time to compile a project, not 38x+!!

So I would like to know what kind of possible problems I might have in my Windows for this exaggerated slowness to happen. I know I ended up installing at least 4 different versions of MinGW; could this have brought the problem?

It's interesting also to notice that when compiling using the -j option and watching the Compile Output log in Qt Creator alongside Process Explorer, there are moments when the compiling simple pauses for 10 seconds or more and the CPU usage drops from its ~100% to close to 5% with nothing happening till it suddenly continues the compilation process. I'm sure this constant pauses are part of the above average time, but I have no idea why MinGW is showing this behaviour.

Upvotes: 4

Views: 4137

Answers (1)

Marged
Marged

Reputation: 10953

You might want to check where the time is spent.

There a lot of tools that allow you to capture what a certain process is doing, I name just two of them:

But to analyze the reports generated by these tools you need a rather deep understanding. If this doesn't help temporarily disable other running services and program step-by-step (if you want to know which program causes the problem) or disable all of them at once. Looking at the spikes of cpu usage that TaskManager or Procexp by sysinternals show might help too to identify those components that block your cpu. If your antivirus is the cause of the collision that makes the compile so slow you can define exceptions, then the antivirus will not scan certain programs or paths.

So perhaps it is easier to first try the compilation process with a disabled antivirus software or even from a clean live boot Windows CD.

Upvotes: 2

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