[Pharo-project] [FFI] ExternalStructure ownership (or not) of memory
Hello all, Suppose I have a pointer to a structure and I do or do not have the responsibility of reclaiming the memory when a corresponding ExternalStructure sub-instance is finalized. How do I distinguish the two cases? One idea I had is to explicitly set the handle to nil if I do not own the memory, but (please correct me if I'm wrong), I can't do that while I'm still using the instance because it will presumably use the handle in accessing the fields, right? Looking at implementors of #isExternalAddress, maybe the idea is to use a byte array to make a copy of memory and an address to refer to it. What should I be asking? :) Bill
In dealing with the case where you have a Smalltalk object that is paired to a external object where you want to ensure both are freed (at some point). There are two choices (a) You store a reference (somehow) to the external object in your smalltalk object. This can be some sort of index number that the external logic understands how to turn that into a reference to the memory, or you store the bytes for a memory pointer in the smalltalk instance. Don't forget issues with 32 or 64 bit memory addresses. You then always send your smalltalk object a release method that ensures it's external memory usage is cleaned up, either by using the memory pointer bytes or the index handle, when you decide to dispose of the smalltalk object. The release method then talks to the external interface to dispose of the external memory. (b) Like above, but you use Finalization to ensure external memory gets cleaned up when the Smalltalk object goes away. On 2010-04-02, at 5:17 PM, Schwab,Wilhelm K wrote:
Hello all,
Suppose I have a pointer to a structure and I do or do not have the responsibility of reclaiming the memory when a corresponding ExternalStructure sub-instance is finalized. How do I distinguish the two cases? One idea I had is to explicitly set the handle to nil if I do not own the memory, but (please correct me if I'm wrong), I can't do that while I'm still using the instance because it will presumably use the handle in accessing the fields, right?
Looking at implementors of #isExternalAddress, maybe the idea is to use a byte array to make a copy of memory and an address to refer to it.
What should I be asking? :)
Bill
-- =========================================================================== John M. McIntosh <johnmci@smalltalkconsulting.com> Twitter: squeaker68882 Corporate Smalltalk Consulting Ltd. http://www.smalltalkconsulting.com ===========================================================================
I would suggest that you only register a finalizer for objects where you *do* have responsibility to reclaim them. There are no implicit finalizers registered for any subclasses of ExternalObject by default - the only thing that happens is that all handles are cleared when the image is restarted. Cheers, - Andreas On 4/2/2010 5:17 PM, Schwab,Wilhelm K wrote:
Hello all,
Suppose I have a pointer to a structure and I do or do not have the responsibility of reclaiming the memory when a corresponding ExternalStructure sub-instance is finalized. How do I distinguish the two cases? One idea I had is to explicitly set the handle to nil if I do not own the memory, but (please correct me if I'm wrong), I can't do that while I'm still using the instance because it will presumably use the handle in accessing the fields, right?
Looking at implementors of #isExternalAddress, maybe the idea is to use a byte array to make a copy of memory and an address to refer to it.
What should I be asking? :)
Bill
Andreas, So ExternalStructure>>free is not invoked by default? Sady to say, I never even considered that possibility. Bill -----Original Message----- From: pharo-project-bounces@lists.gforge.inria.fr [mailto:pharo-project-bounces@lists.gforge.inria.fr] On Behalf Of Andreas Raab Sent: Friday, April 02, 2010 8:24 PM To: The general-purpose Squeak developers list Cc: Pharo-project@lists.gforge.inria.fr Subject: Re: [Pharo-project] [FFI] ExternalStructure ownership (or not) of memory I would suggest that you only register a finalizer for objects where you *do* have responsibility to reclaim them. There are no implicit finalizers registered for any subclasses of ExternalObject by default - the only thing that happens is that all handles are cleared when the image is restarted. Cheers, - Andreas On 4/2/2010 5:17 PM, Schwab,Wilhelm K wrote:
Hello all,
Suppose I have a pointer to a structure and I do or do not have the responsibility of reclaiming the memory when a corresponding ExternalStructure sub-instance is finalized. How do I distinguish the two cases? One idea I had is to explicitly set the handle to nil if I do not own the memory, but (please correct me if I'm wrong), I can't do that while I'm still using the instance because it will presumably use the handle in accessing the fields, right?
Looking at implementors of #isExternalAddress, maybe the idea is to use a byte array to make a copy of memory and an address to refer to it.
What should I be asking? :)
Bill
_______________________________________________ Pharo-project mailing list Pharo-project@lists.gforge.inria.fr http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project
On 4/2/2010 8:37 PM, Schwab,Wilhelm K wrote:
Andreas,
So ExternalStructure>>free is not invoked by default? Sady to say, I never even considered that possibility.
It's not. Memory is cheap :-) Cheers, - Andreas
-----Original Message----- From: pharo-project-bounces-bM+ny+RY8h+a+bCvCPl5/gCzwTLBPCX0@public.gmane.org [mailto:pharo-project-bounces-bM+ny+RY8h+a+bCvCPl5/gCzwTLBPCX0@public.gmane.org] On Behalf Of Andreas Raab Sent: Friday, April 02, 2010 8:24 PM To: The general-purpose Squeak developers list Cc: Pharo-project-bM+ny+RY8h+a+bCvCPl5/gCzwTLBPCX0@public.gmane.org Subject: Re: [Pharo-project] [FFI] ExternalStructure ownership (or not) of memory
I would suggest that you only register a finalizer for objects where you *do* have responsibility to reclaim them. There are no implicit finalizers registered for any subclasses of ExternalObject by default - the only thing that happens is that all handles are cleared when the image is restarted.
Cheers, - Andreas
On 4/2/2010 5:17 PM, Schwab,Wilhelm K wrote:
Hello all,
Suppose I have a pointer to a structure and I do or do not have the responsibility of reclaiming the memory when a corresponding ExternalStructure sub-instance is finalized. How do I distinguish the two cases? One idea I had is to explicitly set the handle to nil if I do not own the memory, but (please correct me if I'm wrong), I can't do that while I'm still using the instance because it will presumably use the handle in accessing the fields, right?
Looking at implementors of #isExternalAddress, maybe the idea is to use a byte array to make a copy of memory and an address to refer to it.
What should I be asking? :)
Bill
_______________________________________________ Pharo-project mailing list Pharo-project-bM+ny+RY8h+a+bCvCPl5/gCzwTLBPCX0@public.gmane.org http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project
Andreas, Humor aside, it is an important consideration for a system that is to be able to run for any length of time. So far, I appear to be having good results in that area (yup, my servers are still running), but I am working on something that could turn into a real resource hog if it does not clean up after itself. I *think* the cleanup is limited to other wrapper objects, and the structs are largely just a convenience for accessing memory allocated elsewhere - I think ~:0 Thanks! Bill -----Original Message----- From: pharo-project-bounces@lists.gforge.inria.fr [mailto:pharo-project-bounces@lists.gforge.inria.fr] On Behalf Of Andreas Raab Sent: Saturday, April 03, 2010 12:33 AM To: The general-purpose Squeak developers list; Pharo Development Subject: Re: [Pharo-project] [FFI] ExternalStructure ownership (or not) of memory On 4/2/2010 8:37 PM, Schwab,Wilhelm K wrote:
Andreas,
So ExternalStructure>>free is not invoked by default? Sady to say, I never even considered that possibility.
It's not. Memory is cheap :-) Cheers, - Andreas
-----Original Message----- From: pharo-project-bounces-bM+ny+RY8h+a+bCvCPl5/gCzwTLBPCX0@public.gmane.or g [mailto:pharo-project-bounces-bM+ny+RY8h+a+bCvCPl5/gCzwTLBPCX0@public. gmane.org] On Behalf Of Andreas Raab Sent: Friday, April 02, 2010 8:24 PM To: The general-purpose Squeak developers list Cc: Pharo-project-bM+ny+RY8h+a+bCvCPl5/gCzwTLBPCX0@public.gmane.org Subject: Re: [Pharo-project] [FFI] ExternalStructure ownership (or not) of memory
I would suggest that you only register a finalizer for objects where you *do* have responsibility to reclaim them. There are no implicit finalizers registered for any subclasses of ExternalObject by default - the only thing that happens is that all handles are cleared when the image is restarted.
Cheers, - Andreas
On 4/2/2010 5:17 PM, Schwab,Wilhelm K wrote:
Hello all,
Suppose I have a pointer to a structure and I do or do not have the responsibility of reclaiming the memory when a corresponding ExternalStructure sub-instance is finalized. How do I distinguish the two cases? One idea I had is to explicitly set the handle to nil if I do not own the memory, but (please correct me if I'm wrong), I can't do that while I'm still using the instance because it will presumably use the handle in accessing the fields, right?
Looking at implementors of #isExternalAddress, maybe the idea is to use a byte array to make a copy of memory and an address to refer to it.
What should I be asking? :)
Bill
_______________________________________________ Pharo-project mailing list Pharo-project-bM+ny+RY8h+a+bCvCPl5/gCzwTLBPCX0@public.gmane.org http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project
_______________________________________________ Pharo-project mailing list Pharo-project@lists.gforge.inria.fr http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project
participants (3)
-
Andreas Raab -
John M McIntosh -
Schwab,Wilhelm K