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D - GC: does it work?

reply imr1984 <imr1984_member pathlink.com> writes:
i made a program that frequently uses lots of dynamic memory, and set a WM_TIMER
message to call gc.fullCollect(). but it never seems to actually free any memory
according to the task manager.
Mar 04 2004
parent reply Vathix <vathix dprogramming.com> writes:
imr1984 wrote:


 i made a program that frequently uses lots of dynamic memory, and set a
WM_TIMER
 message to call gc.fullCollect(). but it never seems to actually free any
memory
 according to the task manager.
 


I think it just reclaims the memory to a free pool, allowing you to 
reuse it without allocating more from the OS. I do the same WM_TIMER 
thing sometimes, and you can get GC stats from std.gc.getStats() (not 
standard).

-- 
Christopher E. Miller
Mar 04 2004
parent reply Stewart Gordon <smjg_1998 yahoo.com> writes:
Vathix wrote:

<snip>

 I think it just reclaims the memory to a free pool, allowing you to  
 reuse it without allocating more from the OS. I do the same WM_TIMER 
 thing sometimes, and you can get GC stats from std.gc.getStats() 
 (not standard).


So, which little-known compiler has this?

Stewart.

-- 
My e-mail is valid but not my primary mailbox, aside from its being the
unfortunate victim of intensive mail-bombing at the moment.  Please keep
replies on the 'group where everyone may benefit.
Mar 05 2004
parent reply J Anderson <REMOVEanderson badmama.com.au> writes:
Stewart Gordon wrote:


 Vathix wrote:

 <snip>


 I think it just reclaims the memory to a free pool, allowing you to  
 reuse it without allocating more from the OS. I do the same WM_TIMER 
 thing sometimes, and you can get GC stats from std.gc.getStats() (not 
 standard).



 So, which little-known compiler has this?

 Stewart.


I think that most compilers do this (including C++).  The only one I can 
think of that frees memory back to the OS is Eiffel.

-- 
-Anderson: http://badmama.com.au/~anderson/
Mar 05 2004
parent reply Stewart Gordon <smjg_1998 yahoo.com> writes:
J Anderson wrote:


 Stewart Gordon wrote:

 Vathix wrote:
 <snip>

 I think it just reclaims the memory to a free pool, allowing you to  
 reuse it without allocating more from the OS. I do the same WM_TIMER 
 thing sometimes, and you can get GC stats from std.gc.getStats() (not 
 standard).


 So, which little-known compiler has this?


 
 I think that most compilers do this (including C++). 


I said "has this".  As in the misnamed std.gc.getStats.


 The only one I can think of that frees memory back to the OS is Eiffel.


You mean I'll have to write in this if I want my program to be able to 
let go of some memory so that other programs can do their business?

Stewart.

-- 
My e-mail is valid but not my primary mailbox, aside from its being the 
unfortunate victim of intensive mail-bombing at the moment.  Please keep 
replies on the 'group where everyone may benefit.
Mar 05 2004
next sibling parent reply Vathix <vathix dprogramming.com> writes:
Stewart Gordon wrote:


 J Anderson wrote:
 

 Stewart Gordon wrote:


 Vathix wrote:
 <snip>


 I think it just reclaims the memory to a free pool, allowing you to  
 reuse it without allocating more from the OS. I do the same WM_TIMER 
 thing sometimes, and you can get GC stats from std.gc.getStats() 
 (not standard).



 So, which little-known compiler has this?



 I think that most compilers do this (including C++). 


 
 
 I said "has this".  As in the misnamed std.gc.getStats.
 

 The only one I can think of that frees memory back to the OS is Eiffel.


 
 
 You mean I'll have to write in this if I want my program to be able to 
 let go of some memory so that other programs can do their business?
 
 Stewart.
 


The OS might swap the memory out (as that memory is not being accessed 
?) so that other programs get it, but I'm no expert on how this occurs. 
That doesn't really help, does it :p

-- 
Christopher E. Miller
Mar 05 2004
parent =?ISO-8859-1?Q?Sigbj=F8rn_Lund_Olsen?= <sigbjorn lundolsen.net> writes:
Vathix wrote:


 Stewart Gordon wrote:
 

 J Anderson wrote:


 Stewart Gordon wrote:


 Vathix wrote:
 <snip>


 I think it just reclaims the memory to a free pool, allowing you 
 to  reuse it without allocating more from the OS. I do the same 
 WM_TIMER thing sometimes, and you can get GC stats from 
 std.gc.getStats() (not standard).




 So, which little-known compiler has this?




 I think that most compilers do this (including C++). 




 I said "has this".  As in the misnamed std.gc.getStats.


 The only one I can think of that frees memory back to the OS is Eiffel.




 You mean I'll have to write in this if I want my program to be able to 
 let go of some memory so that other programs can do their business?

 Stewart.


 
 The OS might swap the memory out (as that memory is not being accessed 
 ?) so that other programs get it, but I'm no expert on how this occurs. 
 That doesn't really help, does it :p
 


There does tend to be an overall limit to how much an OS will allocate 
(in my case 1.5gb, 512mb ram + 1gb swap), swap and all. It could be 
handy to have something to call when one explicitly does want to free 
memory back to the OS, not just to the GC. Let's say I ran a program 
that used 1.2gb at one point for some scientific calculation, and then 
for the next bit only really needs 50mb, but lots and lots of CPU 
time... Would 200mb of my actual physical memory continue to be 
allocated to this program? That would be a little counter-intuitive, imo.

AFAIK (from the D docs) D allows explicitly 'free'ing of objects, ie the 
freeing of objects that will call the object's destructors *at that 
time* and not wait for the GC to plod along at its convenience... Which 
is a very useful feature if its absolutely imperative to free a resource 
at that given time. I really liked this compromising attitude, where the 
GC will sort you out most of the time, but if you tell the GC you know 
what you want, it'll let you have your way. In this case, with memory 
allocation, if the GC does in fact not release its RAM back to the OS at 
any time, wouldn't it make some sense to have a method of explicitly 
telling it to?

Cheers,
Sigbjørn Lund Olsen
(But I May Be Wrong)
Mar 12 2004
prev sibling next sibling parent J Anderson <REMOVEanderson badmama.com.au> writes:
Stewart Gordon wrote:


 J Anderson wrote:


 Stewart Gordon wrote:


 Vathix wrote:
 <snip>


 I think it just reclaims the memory to a free pool, allowing you 
 to  reuse it without allocating more from the OS. I do the same 
 WM_TIMER thing sometimes, and you can get GC stats from 
 std.gc.getStats() (not standard).



 So, which little-known compiler has this?



 I think that most compilers do this (including C++). 



 I said "has this".  As in the misnamed std.gc.getStats.


 The only one I can think of that frees memory back to the OS is Eiffel.



 You mean I'll have to write in this if I want my program to be able to 
 let go of some memory so that other programs can do their business?

 Stewart.


If the memory is not being used it'll probably be swapped out to a page 
file on the hardrive.

-- 
-Anderson: http://badmama.com.au/~anderson/
Mar 05 2004
prev sibling parent Ilya Minkov <minkov cs.tum.edu> writes:
Stewart Gordon schrieb:


 You mean I'll have to write in this if I want my program to be able to 
 let go of some memory so that other programs can do their business?


Eiffel won't help either, since it would work on some C runtime anyway. :>

Walter promised that D's GC would return memory to OS page-wise as it 
gets free.

-eye
Mar 05 2004