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DLL code is much slower than main program code
Posted: Sun Aug 04, 2024 2:43 pm
by Jens-Arne
Hello,
I've written some quite complicated code that deals with custom drawing list views. It is super fast when it is compiled into a main exe file, but when it is situated in a dll it slows down to 1/10 of the original speed or so. No changes to the code, doesn't matter if it is 32bit or 64bit, native or C-backend.
The code makes extensive use of Windows API calls. I couldn't pin it down to a specific bit of code, it is just incredibly slow over the whole thing even at the beginning when variables are set up etc. for no apparent reason. Does anybody have a clue what could be the problem here? Natively compiled code should be at exactly the same speed, no matter if it was located in the main exe or in a dll - code is code.
One last thing: Debugger, purifier and enhancer are disabled both in the main program and in the dll.
Regards, Jens-Arne
Re: DLL code is much slower than main program code
Posted: Sun Aug 04, 2024 3:40 pm
by Caronte3D
Maybe you are making an huge amount of dll calls, that should be slower than direct execution?
(I don't know, just thinking)
Re: DLL code is much slower than main program code
Posted: Sun Aug 04, 2024 4:07 pm
by Jens-Arne
@Caronte3D: Thank you for your reply, but no, this is not at all the case here. At first things are set up with a bunch of dll calls, but then everything runs "on its own" through a subclass function. That is the place where all the drawing takes place, and this subclass function is called by Windows just the same way in an exe as it is in a dll. That's what makes things so very much puzzling.
Moreover, function calls should be equally fast in the exe code and in the dll code. It's always the same register shuffling taking place with function calls, but the technique is all the same. Save registers, call entry point (whereever it might reside in memory), restore registers.
Re: DLL code is much slower than main program code
Posted: Sun Aug 04, 2024 10:14 pm
by chi
If you don't use AttachThread/DetachThread you could try
Code: Select all
ProcedureDLL AttachProcess(Instance)
DisableThreadLibraryCalls_(Instance)
EndProcedure
But without any code, just a hunch...
Re: DLL code is much slower than main program code
Posted: Mon Aug 05, 2024 7:03 am
by Jens-Arne
@chi: Interesting function, didn't know this one, thank you. But it makes no difference in this case. As far as I understand it only changes the behaviour of the DLL when it is loaded/unloaded, and especially when this is done by a thread. At least my test program is single-threaded and (un)loads the DLL only once.
Re: DLL code is much slower than main program code
Posted: Mon Aug 05, 2024 12:51 pm
by chi
...and you followed the rules? (Help/Building a DLL)
Code: Select all
Notes about creating DLL's:
- The declaration of arrays, lists or map with Dim, NewList or NewMap must always be done inside the procedure AttachProcess.
- Don't write program code outside procedures. The only exception is the declaration of variables or structures.
- Default values in procedure parameters have no effect.
- DirectX initialization routines must not be written in the AttachProcess procedure.
Other than that, create a stripped down version of your dll and trial & error
. Use OutputDebugString_("..") and
DebugView /
DebugView++ inside your dll to track the flow or check the timing.
Re: DLL code is much slower than main program code
Posted: Mon Aug 05, 2024 4:12 pm
by Jens-Arne
All rules followed. No change.
Re: DLL code is much slower than main program code
Posted: Mon Aug 05, 2024 5:43 pm
by HeX0R
Antivir disabled?
Re: DLL code is much slower than main program code
Posted: Mon Aug 05, 2024 8:57 pm
by Jens-Arne
Antivir was not the problem.
I found the bottleneck and got rid of it. But one thing remains: It wasn't a bottleneck in plain PB code but got extremely slow in a PB-DLL. I still don't know why. it was down to the fact that I was assembling a string out of substrings with a delimiter only to rip it apart again using StringField. But again, it is fast in an ordinary EXE and extremely slow in a DLL. The exact same code. That remains strange and a little worrysome. Is there something askew with string handling in PB-DLLs?
Re: DLL code is much slower than main program code
Posted: Mon Aug 05, 2024 9:04 pm
by AZJIO
Make two test cases to prove it. One for the executable file, the other for the dll.
Without seeing the code, it is impossible to take your word for it. And to solve a problem that doesn't exist
Re: DLL code is much slower than main program code
Posted: Mon Aug 05, 2024 9:43 pm
by Jens-Arne
Of course you're right on that. I'll try. But not today. Maybe I'm wrong after all, I just need a little rest to reconsider and think about the way to prove or falsify it with as simple a piece of code as possible.
Re: DLL code is much slower than main program code
Posted: Mon Sep 09, 2024 6:49 pm
by Thorium
Do you use the C-Backend with optimization?
If yes, disable it and see if the standalone is a as slow as the dll.
The only guess i have is that the compiler does some optimization magic and inlines a bunch of stuff, which it can't do on the dll because it's dynamically linked in.
Re: DLL code is much slower than main program code
Posted: Mon Sep 09, 2024 10:47 pm
by Jens-Arne
No, it was the native compiler without optimizations. As I progressed with the work on the project I felt at some point like the DLL wasn't slower than the normal code anymore. I know that this is a little fuzzy but at the beginning the slowdown was dramatic, lateron it wasn't that percievable anymore. It might really have been my fault, that's my best guess at the moment. Honestly I am unable to supply some test code that reproduces this experience reliably.