Re: [rvm-research] about the lock() in freelist

Hi,Robin

Thank you very much. I understand how the lock works.
I'm sorry for response so late.


On Thu, Jun 11, 2015 at 9:18 AM, Robin Garner <[email protected]> wrote:

>
> You will see that the lock() method is inherited from the PageResource
> class, which acquires a lock on the instance variable 'lock'.  This
> tells you that what is being locked is this specific instance of
> FreeListPageResource.  The only threads blocked by this lock are ones
> that a) are allocating in the same space, and b) have to allocate fresh
> blocks from the PageResource.  Blocks are sized so as to make (b)
> infrequent.
>
> [1] http://users.cecs.anu.edu.au/~steveb/downloads/pdf/mmtk-icse-2004.pdf

1)
Yes, The lock()  used in the FreeListPageResource.java/allocPages  is
defined in PageResouce.java
private final Lock lock

It's not a static object. Every space has its own pr(protected
PageResource pr; ),
so only the threads in the same Space (such as  threads in the immix)
will be synchronized by this lock.

But the lock in the Map.java is defined as:
private static final Lock lock = VM.newLock("Map lock");

It's a static object. So every thread no matter which Space it belongs
to will be synchronized by this static lock.
And the Map.lock is used to synchronize the Chunk allocate.

2)
I have read the paper ,but I'm still confused about  how to judge
which method will be accessed concurrently by multi-threads ,
which method will only be accessed by the main thread.

I know that , every thread start by call the function startoff() in
the RVMThread.java,
then these threads will run concurrently.
So, every method in this path(  start from startoff() ) will be
accessed by multi-threads ?

I'm a little confused about the architecture of jikesrvm's  multi-threads model.


-- 
ChenXi.Wang

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