Re: [rvm-research] to utilize methods in syscall

> Liangliang Tong wrote:
>  
>> Dear all,
>>
>> In org.mmtk.plan.generational.Gen.java, I want to modify the vmRequest
>> to request for an explicit region of memory, like the following:
>>    private static final VMRequest vmRequest =
>> VMRequest.create(sysCall.sysMalloc(1 << 20),  Extent.fromIntSignExtend(1
>> << 20));
>> correspondingly I add a new import statement:
>>  import static org.jikesrvm.runtime.SysCall.sysCall;
>>
>> Yet when I complied the generational copy plan, it prompts these errors:
>> compile-mmtk:
>>     [javac] Compiling 1 source file to
>> /home/lltong/jikesrvm/target/mmtk/classes
>>     [javac]
>> /home/lltong/jikesrvm/MMTk/src/org/mmtk/plan/crgenerational/CRGen.java:33:
>> package org.jikesrvm.runtime does not exist
>>     [javac] import static org.jikesrvm.runtime.SysCall.sysCall;
>>     [javac]                                   ^
>>     [javac]
>> /home/lltong/jikesrvm/MMTk/src/org/mmtk/plan/crgenerational/CRGen.java:33:
>> static import only from classes and interfaces
>>     [javac] import static org.jikesrvm.runtime.SysCall.sysCall;
>>     [javac] ^
>>     [javac]
>> /home/lltong/jikesrvm/MMTk/src/org/mmtk/plan/crgenerational/CRGen.java:91:
>> cannot find symbol
>>     [javac] symbol  : variable sysCall
>>     [javac] location: class org.mmtk.plan.crgenerational.CRGen
>>
>> Why should this happen? Thanks in advance.
>>
>>  
>>    
> Hi Liangliang,
>
> As far as I can see, you are trying to request a 1MB chunk of memory,
> and you don't care where in the heap it is.  Is this right ?
>
>
> MMTk uses the 'Space' class to abstract over various ways to allocate
> memory.  If you simply want a 1MB chunk of raw memory, then you can do
>
>   RawPageSpace mySpace = new RawPageSpace("mySpace", Integer.MAX_VALUE,
> VMRequest.create());
>   Address chunkAddr = mySpace.acquire(1<<(20-LOG_BYTES_IN_PAGE));
>
> If you're using memory as storage for your collector, you should
> probably allocate it in the existing metaDataSpace.  If you're
> allocating it to give to the mutator, you should probably define a new
> space for it.
>
> Note that a VMRequest is simply a way to communicate your virtual memory
> layout requirements to the Space class, and passing it a chunk of
> 'malloc'ed memory doesn't make a great deal of sense.  In fact MMTk
> itself generally takes the place of 'malloc' in the virtual machine.
>
>
> The reason you can't directly call sysMalloc from MMTk is that MMTk
> separates itself from JikesRVM (and its various other host environments)
> via the org.mmtk.vm package (the VM interface).  In order to call a new
> method on the JikesRVM side of the fence you need to:
>
> - Choose an interface class to host the method (eg org.mmtk.vm.Memory)
> - Add an abstract method to the interface class
> - Add a concrete method to the implementation on the VM side of the
> fence (for JikesRVM that is org.jikesrvm.mm.mmtk, in the
> MMTk/ext/vm/jikesrvm directory)
>
> but I think it would generally be a bad idea for you to allocate memory
> for JikesRVM using sysMalloc.
>
> Regards,
> Robin
>
>
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