Controlling the garbage collector (GC) at RT?

[Martin Egholm Nielsen]

Hi Hans,

> There are also a number of environment variables that have some
> impact on this.  Depending on your application, this may be
> easier than Bryce's suggestion or completely useless.
> They are documented in
> 
> gcc/boehm-gc/doc/README.environment
> 
> You might get the desired effect by setting GC_INITIAL_HEAP_SIZE
> to something near what you expect the final size to be.  
Deja vu! :-)
We've been there before (http://gcc.gnu.org/ml/java/2004-11/msg00143.html).
But all these environments are for initial configuration, so I think I
may go with Bryce's suggestion instead.

And in relation to that thread, what is the effect of adjusting
GC_free_space_divisor? (Maybe I should take that back in the old thread)

> The collector tries to take such an explicit setting as a strong hint
> that it should actually be using that much of the heap before 
> collecting.
Sure, but I'm trying to avoid GC while the application is in a
"critical" state. Doing as you suggest, wouldn't that just make things
worse in case it starts collecting when it reaches the roof?
Then there's a lot to collect...

Am I the only one that think a GCJ interface for controlling the GC
would be neat?

// Martin

>>-----Original Message-----
>>From: java-owner@gcc.gnu.org 
>>[mailto:java-owner@gcc.gnu.org]On Behalf Of
>>Bryce McKinlay
>>Sent: Wednesday, February 02, 2005 12:07 PM
>>To: Martin Egholm Nielsen
>>Cc: java@gcc.gnu.org
>>Subject: Re: Controlling the garbage collector (GC) at RT?
>>
>>
>>Martin Egholm Nielsen wrote:
>>
>>
>>>Does GCJ somehow support controlling the GC at runtime?
>>>That is, e.g. configure it for different behaviour:
>>>
>>>1) Run as you usually do
>>>2) Please do not not run unless it is really needed
>>>3) Don't run at all (let application die if it must)
>>>
>>>Point 2 is actually what I'm after, but I'm reconsidering (as I'm 
>>>writing) if it actually makes any sense.
>>
>>
>>The Boehm GC has the functions GC_enable() and GC_disable() 
>>which should 
>>do basically what you want. We don't have an interface to call these 
>>directly from Java, however, you could perhaps add your own interface 
>>and call the GC functions directly via CNI.
>>
>>See boehm-gc/include.gc.h
>>
>>Bryce
>>
>>
> 
>