[fpc-pascal] How to find where my app consumes CPU?

[Travis Siegel]

I'm not positive, but I'm pretty sure the sleep command in linux does 
not behave the same way it does in windows.

As you know, in windows, a sleep command (even if delivered with a 
parameter of 0) gives up time slices to other programs on the system.  
This does not appear to be the case on linux.

On linux, the sleep command simply suspends the process for the 
specified amount of time, but so far as I can tell, does nothing for 
unused cpu cycles.

I've done a little digging, but I can't find any way on linux to give 
away unused cpu cycles.

Perhaps the linux task switcher doesn't allow for this capability?


On 5/18/2021 3:59 PM, Bo Berglund via fpc-pascal wrote:
> I have a pretty sizable console app written with Delphi 15 years ago but ported
> to Linux using FreePascal (3.2.0) with Lazarus (2.0.12) as IDE. It runs as a
> systemd service on a Raspberry Pi3.
>
> Basically it is a scheduler, which checks every minute if there is a task to
> run, otherwise it waits for the next minute to pass.
>
> Meanwhile in another thread there is a TCP/IP socket server active for
> communicating with the app over the network. So it is listening for incoming
> connections.
>
> This is working seemingly OK, but today when I checked the RPi I found using top
> that it was running 11% CPU, which is strange because it has nothing to do at
> the moment.
>
> I have tried to be as conservative as possible regarding wait loops etc so in
> such loops I always have a sleep() call, which in my Windows experience used to
> stop excessive CPU usage.
>
> So I was surprised to find the high CPU usage and now I am at a loss on how to
> find *where* this is happening...
>
> Any ideas on how to proceed?
> Is there some Lazarus way to find this?
> (But I cannot really run the application in service mode from within Lazarus...)
>
>