RFR (L): 8076454, 8076289 and 8076452: removing SharedHeap
Bengt Rutisson
bengt.rutisson at oracle.com
Thu Apr 2 11:11:27 UTC 2015
Hi StefanK,
Thanks for looking at this!
Comments inline.
On 2015-04-01 17:14, Stefan Karlsson wrote:
> Hi Bengt,
>
> On 2015-04-01 14:30, Bengt Rutisson wrote:
>>
>> Hi everyone,
>>
>> Could I have a couple of reviews for these three patches to remove
>> SharedHeap?
>>
>> I'm sending all three patches in the same email because I think they
>> are closely related. But I am planning to push them at three separate
>> changes.
>>
>> JDK-8076454: Clean up/move things out of SharedHeap
>> https://bugs.openjdk.java.net/browse/JDK-8076454
>> http://cr.openjdk.java.net/~brutisso/8076454/webrev.00/
>>
>>
>> JDK-8076289: Move the StrongRootsScope out of SharedHeap
>> https://bugs.openjdk.java.net/browse/JDK-8076289
>> http://cr.openjdk.java.net/~brutisso/8076289/webrev.00/
>>
>>
>> JDK-8076452: Remove SharedHeap
>> https://bugs.openjdk.java.net/browse/JDK-8076452
>> http://cr.openjdk.java.net/~brutisso/8076452/webrev.00/
>>
>>
>>
>> Some more details about the changes:
>>
>> JDK-8076454 contains many small changes. Here's the steps I took to
>> complete the patch. It may be easier to review each step of the way:
>>
>> http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-remove_SharedHeap_gcprologue/
>>
>> This removes the pure virtual implementations of
>> SharedHeap::gc_prologue() and SharedHeap::gc_epilogue() since there
>> are no callers of these methods. All calls are directly to the
>> concrete subclasses.
>>
>> http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-remove_SharedHeap_set_barrier_set/
>>
>> This removes SharedHeap::set_barrier() and instead inlines the code
>> in G1CollectedHeap and GenCollectedHeap similarly to what
>> ParallelScavengeHeap already does.
>>
>> http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-move_post_initialized_and_ref_init/
>>
>> SharedHeap::post_initialize() was just forwarding to
>> CollectedHeap::post_initialize() and adding a call to
>> ref_processing_init(). Moved this down to the concrete sub classes.
>>
>> http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-remove_SharedHeap_no_gc_in_progress/
>>
>> no_gc_in_progress() is only used in GenCollectedHeap so it is enough
>> that it is declared there.
>>
>> http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-remove_SharedHeap_space_iterate/
>>
>> space_iterate() was dead code.
>>
>> http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-remove_SharedHeap_oop_iterate/
>>
>> oop_iterate() is already declared pure virtual in CollectedHeap, so
>> no need to have it in SharedHeap too.
>>
>> http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-remove_SharedHeap_space_containing/
>>
>> There were no callers of SharedHeap::space_containing(). No need to
>> have a virtual method in SharedHeap. Enough to declare the methods in
>> the concrete sub classes.
>>
>> http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-cleanup_includes_and_friends/
>>
>> Just some cleanups of includes and friend declarations. Not really
>> relevant as the file will be completely removed by JDK-8076452.
>>
>> http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-remove_SharedHeap_set_par_threads/
>>
>> SharedHeap::set_par_threads() only introduced an assert compared to
>> what CollectedHeap::set_par_threads() already does. The assert is
>> only relevant in the GenCollectedHeap case. So I moved the assert
>> down to that class.
>>
>> http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-move_workers/
>> Move the instance variable to hold the FlexibleWorkGang (_workers)
>> down to the concrete sub classes. Only two lines of common code, so
>> hardly worth sharing.
>>
>> http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-product-fix/
>> I had a mistake for product builds regarding
>> set_heap_lock_held_for_gc().
>>
>>
>>
>> JDK-8076289 moves the StrongRootsScope class out to its own file.
>>
>> http://cr.openjdk.java.net/~brutisso/8076289/webrev.00-remove_StrongRootsScope_sh/
>>
>> The StrongRootsScope no longer makes use of its SharedHeap instance
>> variable, so it can be removed and the constructor does not have to
>> take it as a parameter.
>>
>> http://cr.openjdk.java.net/~brutisso/8076289/webrev.00-move_StrongRootsScope/
>>
>> Move the StrongRootsScope out to its own files and to the global name
>> space.
>>
>> http://cr.openjdk.java.net/~brutisso/8076289/webrev.00-move_MarkScope/
>> Move the super class of StrongRootsScope, MarkScope, into the same
>> files.
>>
>> I would like to follow this change up with a couple of things. I
>> would like to rename StrongRootsScope to something like
>> RootProcessingScope since we no longer use it purely for strong
>> roots. I would like to rename MarkScope to something like
>> NMethodScope. And I think ParallelScavenge could use MarkScope
>> directly instead of introducing ParStrongRootsScope. But I would like
>> to do these changes as a separate patch.
>>
>>
>> JDK-8076452 is pretty much just one patch to get rid of all reference
>> to SharedHeap now that it is empty after the above changes.
>
> Thanks for providing the incremental patches, it made the patches much
> easier to review.
>
> http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-remove_SharedHeap_set_barrier_set/
>
>
> All three heap implementations perform the same sequence:
> + _barrier_set = bs;
> + oopDesc::set_bs(bs);
>
> I'd prefer if we could move that to a function in CollectedHeap.
Done.
http://cr.openjdk.java.net/~brutisso/8076454/webrev-remove_SharedHeap_set_barrier_set.01/
http://cr.openjdk.java.net/~brutisso/8076454/webrev-remove_SharedHeap_set_barrier_set.00-01.diff/
>
>
> http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-move_post_initialized_and_ref_init/
>
>
> http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-move_post_initialized_and_ref_init/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp.udiff.html
>
>
> + // Does operations required after initialization has been done.
> + void post_initialize();
> +
> // Initialize weak reference processing.
> virtual void ref_processing_init();
>
> The ref_processing_init doesn't have to be virtual anymore.
Done.
http://cr.openjdk.java.net/~brutisso/8076454/webrev-move_post_initialized_and_ref_init.01/
http://cr.openjdk.java.net/~brutisso/8076454/webrev-move_post_initialized_and_ref_init.00-01.diff/
>
>
> http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-remove_SharedHeap_space_iterate/
>
>
> http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-remove_SharedHeap_space_iterate/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp.udiff.html
>
>
> -void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
> - SpaceClosureRegionClosure blk(cl);
> - heap_region_iterate(&blk);
> -}
>
> SpaceClosureRegionClosure isn't used anymore and can be removed.
Done.
http://cr.openjdk.java.net/~brutisso/8076454/webrev-remove_SharedHeap_space_iterate.01/
http://cr.openjdk.java.net/~brutisso/8076454/webrev-remove_SharedHeap_space_iterate.00-01.diff/
>
>
> http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-remove_SharedHeap_oop_iterate/
>
>
> CollectedHeap::oop_iterate and CollectedHeap::oop_iterate_no_header
> are only used by CMS. We might want to move those functions to
> GenCollectedHeap.
Done.
http://cr.openjdk.java.net/~brutisso/8076454/webrev-remove_SharedHeap_oop_iterate.01/
http://cr.openjdk.java.net/~brutisso/8076454/webrev-remove_SharedHeap_oop_iterate.00-01.diff/
>
>
> http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-remove_SharedHeap_space_containing/
>
>
> The few usages of space_containing in G1 could be replaced with
> heap_region_containing.
Done.
http://cr.openjdk.java.net/~brutisso/8076454/webrev-remove_SharedHeap_space_containing.01/
http://cr.openjdk.java.net/~brutisso/8076454/webrev-remove_SharedHeap_space_containing.00-01.diff/
>
>
> http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-move_workers/
>
> + if (UseConcMarkSweepGC) {
> + _workers = new FlexibleWorkGang("GC Thread", ParallelGCThreads,
> + /* are_GC_task_threads */true,
> + /* are_ConcurrentGC_threads */false);
> + _workers->initialize_workers();
> + } else {
> + _workers = NULL;
> + }
> }
>
> Could you add a comment that the else statement is for UseSerialGC,
> which doesn't use workers.
Done.
http://cr.openjdk.java.net/~brutisso/8076454/webrev-move_workers.01/
http://cr.openjdk.java.net/~brutisso/8076454/webrev-move_workers.00-01.diff/
>
>
> http://cr.openjdk.java.net/~brutisso/8076454/webrev.00-product-fix/
>
> This is an unrelated change.
Absolutely. This was a mistake. Sorry about that. I removed this patch
from my patch queue.
>
>
> http://cr.openjdk.java.net/~brutisso/8076289/webrev.00-move_StrongRootsScope/
>
>
> http://cr.openjdk.java.net/~brutisso/8076289/webrev.00-move_StrongRootsScope/src/share/vm/runtime/thread.hpp.udiff.html
>
>
> + // If the client meats this spec, then "thread claim parity" will have
> + // the following properties:
> + // a) to return a different value than was returned before the last
> + // call to change_strong_roots_parity, and
> + // c) to never return a distinguished value (zero) with which such
> + // task-claiming variables may be initialized, to indicate "never
> + // claimed".
>
> Could you remove this section? The comments already describe what
> needs to be known.
>
> http://cr.openjdk.java.net/~brutisso/8076289/webrev.00-move_StrongRootsScope/src/share/vm/utilities/workgroup.hpp.udiff.html
>
>
> The comment you moved is too unfocused to aid in the understanding of
> the different parts of the code, and other comments already explain a
> lot of what's said in this file. Could you either remove it, reword it
> or move parts of it to the files where they belong?
>
> http://cr.openjdk.java.net/~brutisso/8076289/webrev.00-move_StrongRootsScope/src/share/vm/memory/strongRootsScope.hpp.html
>
> -
> 30 // Some collectors will perform "process_strong_roots" in parallel.
> 31 // Such a call will involve claiming some fine-grained tasks,
> such as
> 32 // scanning of threads and code blobs.
> 33 // Claiming of these tasks requires that sequential code calls
> 34 // initialization methods to set the claiming code in the right
> 35 // state for parallel task claiming.
> 36 // StrongRootsScope is a way to capture such setup code to make
> 37 // sure that it is executed in the correct way.
>
> Could this comment be reworded into one paragraph?
Removed and updated the comments as you suggested.
http://cr.openjdk.java.net/~brutisso/8076289/webrev-move_StrongRootsScope.01/
http://cr.openjdk.java.net/~brutisso/8076289/webrev-move_StrongRootsScope.00-01.diff/
>
>
> http://cr.openjdk.java.net/~brutisso/8076289/webrev.00-move_MarkScope/
>
> http://cr.openjdk.java.net/~brutisso/8076289/webrev.00-move_MarkScope/src/share/vm/memory/strongRootsScope.hpp.udiff.html
>
>
> Add include allocation.hpp.
>
> Could you move the initialization lists up one line?
Done.
http://cr.openjdk.java.net/~brutisso/8076289/webrev-move_MarkScope.01/
http://cr.openjdk.java.net/~brutisso/8076289/webrev-move_MarkScope.00-01.diff/
>
>
> http://cr.openjdk.java.net/~brutisso/8076452/webrev.00/
>
> This is missing changes to the SA.
Good catch! Fixed.
http://cr.openjdk.java.net/~brutisso/8076452/webrev.01/
http://cr.openjdk.java.net/~brutisso/8076452/webrev.00-01.diff/
>
> I think a few of the includes to collectedHeap.hpp are unnecessary.
That is probably true. I would prefer to clean that up separately since
this patch already contains a lot of changes. My proposed patch only
replaces includes of sharedHeap.hpp with collectedHeap.hpp, which I
think makes it easier to review.
Thanks,
Bengt
>
> Thanks,
> StefanNK
>>
>> Thanks,
>> Bengt
>>
>>
>>
>>
>>
>>
>>
>
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