Re: [rvm-research] Barriers interacting with ForwardingWord in MMTk

  Hi again,

Thanks for your response, Robin, that's very useful since we do want to
make a concurrent copying collector. However, my team and I have one more
question which I believe is due to our misunderstanding of parts of Jikes.

Since I was putting VM.assertions.fail() calls and the like in the
ForwardingWord class, which the semispace collector does use, why did the
benchmarks still run without incident? Is this due to the Dacapo benchmarks
I was choosing to run?(sunflow and avrora) Or are Jikes' internally
implemented assertions somehow different than we are assuming? We have
gotten the same behavior from using VM.sysFail() in the body of the VM, as
well. (no change in vm behavior)

Is there a better way to test if a piece of code executes in JikesRVM?

Thanks again,
Claire.
 ------------------------------
From: Claire Murphy <[email protected]>
Sent: 2/10/2014 4:51 PM
To: General discussion of Jikes RVM design, implementation, issues, and
plans <[email protected]>
Subject: Barriers interacting with ForwardingWord in MMTk

Hello,

My name is Claire, and I'm part of a team of students from Harvey Mudd
College.

We have been working with Jikes RVM, specifically MMTk, and recently I have
been trying to understand how Barriers work in relation to the
ForwardingWord class, and what we need to do to implement forwarding
headers, triggered by barriers, in a custom garbage collector. The
ObjectReference functions that are called in the Barriers seem to be
implemented at runtime by vmmagic, and I do not know where that behavior is
defined.

I have been running Dacapo benchmarks and using the semispace collector,
which I believe should call the ForwardingWord functions if that is what
the Barrier implementations do, though my "VM.assertions._assert"s in the
ForwardingWord functions have had no effect on the benchmarks that I
noticed. I am clearly barking up the wrong tree, so any pointers would be
appreciated.

Thanks!

-Claire

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