Re: [fpc-pascal] Threadvar member field

[Michael Schnell]

On 17.03.2017 23:51, African Wild Dog wrote:


I will have to redesign my classes =(.



Maybe you just can add a field denoting the thread (by n integer) and 
set this when creating an instance, and later just read it for the 
appropriate purpose...


-Michael

___
fpc-pascal maillist  -  fpc-pascal@lists.freepascal.org
http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal

Re: [fpc-pascal] Threadvar member field

[Michael Schnell]

On 17.03.2017 17:13, Karoly Balogh (Charlie/SGR) wrote:
This is actually entirely platform specific. The underlying 
implementation of threadvars is very different for each platform, and 
highly depends both on the CPU arch and the OS.

That might be true.

Last time I checked (several years ago), the fpc implementations did OS 
calls when accessing thread vars with X86 architecture for Windows. This 
is not necessary.  All C compilers I checked don't do this, but use a 
dedicated segment register, even though this (at that time) was not 
documented by Microsoft. Linux C compilers use a dedicated Segment 
register, as well, here its a regular documented feature of the OS. (I 
don't remember what fpc did for Linux at that time.)


Hopefully 64 bit platforms are better (and decently documented) on that 
behalf.


No idea about ARM etc.

-Michael
___
fpc-pascal maillist  -  fpc-pascal@lists.freepascal.org
http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal

Re: [fpc-pascal] Threadvar member field

[African Wild Dog]

2017-03-17 5:50 GMT-03:00 Michael Schnell :

> On 16.03.2017 19:38, African Wild Dog wrote:
>
>> I have a class where its instances are shared between multiple threads.
>> How can I declare one variable per instance per thread?
>>
> Does this really make sense ?
>
> Accessing threadvars (in fpc) costs a lot more CPU cycles (i.e. involves
> an OS call) than accessing normal variables.
>
> Supposedly the way to go is to do per-thread instances of a class, that
> might reference the other classes you want to instantiate.
>
>
I have huge collection of objects (abot 1 million) in memory so if i go
with per-thread instance it will consume the entire memory ram.
I will have to redesign my classes =(.
___
fpc-pascal maillist  -  fpc-pascal@lists.freepascal.org
http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal

Re: [fpc-pascal] Threadvar member field

[Karoly Balogh (Charlie/SGR)]

Hi,

On Fri, 17 Mar 2017, Michael Schnell wrote:

> Accessing threadvars (in fpc) costs a lot more CPU cycles (i.e. involves
> an OS call) than accessing normal variables.

This is actually entirely platform specific. The underlying implementation
of threadvars is very different for each platform, and highly depends both
on the CPU arch and the OS. On some platforms, threadvars are barely
slower than normal ones, other platforms have the large penalty you're
talking about. I agree though that it's still wise to count on the worst
case scenario though.

Charlie
___
fpc-pascal maillist  -  fpc-pascal@lists.freepascal.org
http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal

Re: [fpc-pascal] Threadvar member field

[Michael Schnell]

On 16.03.2017 19:38, African Wild Dog wrote:

I have a class where its instances are shared between multiple threads.
How can I declare one variable per instance per thread?

Does this really make sense ?

Accessing threadvars (in fpc) costs a lot more CPU cycles (i.e. involves 
an OS call) than accessing normal variables.


Supposedly the way to go is to do per-thread instances of a class, that 
might reference the other classes you want to instantiate.


-Michael

___
fpc-pascal maillist  -  fpc-pascal@lists.freepascal.org
http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal

Re: [fpc-pascal] Threadvar member field

[Michael Van Canneyt]

On Thu, 16 Mar 2017, African Wild Dog wrote:


I have a class where its instances are shared between multiple threads.
How can I declare one variable per instance per thread?

The code below does not compile (fpc 3.0.0):

TMyClass = class
public
 threadvar MyValue: Integer;
end;


This is not foreseen as a language construct, you must do this yourself.

Michael.
___
fpc-pascal maillist  -  fpc-pascal@lists.freepascal.org
http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal