CRR (S/M): 7092309: G1: introduce old region set
Bengt Rutisson
bengt.rutisson at oracle.com
Thu Oct 6 11:04:04 UTC 2011
Hi Tony,
This looks good. It will be great to have the old region set for the CR
regarding humungous allocation and concurrent mark start that I am
working on.
Some comments regarding MasterOldRegionSet::check_mt_safety():
The code would be easier (at least for me) to read like this:
if (SafepointSynchronize::is_at_safepoint()) {
guarantee(Thread::current()->is_VM_thread() ||
(_phase == HRSPhaseEvacuation &&
FreeList_lock->owned_by_self()) ||
(_phase == HRSPhaseCleanup &&
OldSets_lock->owned_by_self()), "Master old set MT safety protocol:
safepoint invariants violated");
} else {
guarantee(Heap_lock->owned_by_self(), "Master old set MT safety
protocol: Heap lock must be held if we are not at a safepoint");
}
It would also align nicely with how you structured the comment just
above the guarantee.
Also, the only call to check_mt_safety() that I could find is in
hrs_assert_mt_safety_ok() and there we call it from an assert. If that
is correct, why are then the check_mt_safety() implementations using
guarantees and not asserts?
Thanks,
Bengt
On 2011-10-04 21:54, Tony Printezis wrote:
> Hi all,
>
> This change adds to G1 the facility to keep track of the allocated old
> regions with the HeapRegionSet abstraction and moves us one step
> closer to having all regions being tracked by the same abstraction
> (after this, only the survivor / eden regions remain). I decided to
> work on the old region set now as it was a relatively easy change to
> implement and will make some follow-on CRs easier to implement. The
> webrev is here:
>
> http://cr.openjdk.java.net/~tonyp/7092309/webrev.0/
>
> Most of the changes were straightforward (I largely followed how we
> maintain the humongous region set). The only part which I had to
> slightly revamp was the code that tears down / rebuilds the region
> sets. This small refactoring, though, was worthwhile as it makes that
> code easier to extend in the future (when we introduce the eden /
> survivor lists).
>
> Tony
>
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