[Lazarus] Threads in Lazarus code base

[Mattias Gaertner]

On Wed, 15 Sep 2010 11:49:42 -0300
Luiz Americo Pereira Camara <luizmed at oi.com.br> wrote:

> Mattias Gaertner escreveu:
> > *many IDE parts will become slower (once you start a thread the RTL
> > uses critical sections and especially string handling become much
> > slower).
> 
> If i understand correctly all program will suffer the performance hit, 
> not only the "threaded" part, right?

Correct. As long as another thread runs. When the thread stops all
returns to "normal".

 
> Do you have an idea of how slower string handling would be?

That heavily depends on the string operations you do. I saw two
threads running slower than single threaded.

 
> I'm asking this because i'm planning to make a client of a REST service 
> through http and i choose Synapse to do the communication.
> 
> Since Synapse recommends to use thread to avoid GUI freeze, i planned to 
> use a thread for getting the data.

In this case you have not much choice. 

 
> At the other side this REST server uses JSON as the data format.
> 
> If the thread really affects badly the string handling (and parsing JSON 
> does a lot of it)  i would rethink the strategy and go for an event 
> based http client like lnet.

For performance relevant parts you should use PChar instead of strings.
Even when doing single threaded.

I mentioned the speed difference because this thread is about using
multi threading in the IDE and what advantages/disadvantages this
might have.
The IDE is special in many ways, so don't take the comments of this
thread as a general advice for your own programs.


Mattias