RFR (S): 8195115: G1 Old Gen MemoryPool CollectionUsage.used values don't reflect mixed GC results
Hohensee, Paul
hohensee at amazon.com
Sat Jun 16 19:00:15 UTC 2018
Thanks for the re-review, Erik. New webrev with your fixes:
http://cr.openjdk.java.net/~phh/8195115/webrev.04/
Need another reviewer, please.
Thanks,
Paul
On 6/16/18, 1:25 AM, "Erik Helin" <erik.helin at oracle.com> wrote:
On 06/15/2018 10:21 PM, Hohensee, Paul wrote:
> After some difficulty with the submit cluster, with which Erik helped me out, the patch passes. It also passed fastdebug hotspot tier 1 testing on my Mac laptop, which former includes the new test.
>
> I had to increase -Xmx and -Xms to 12m in order to get TestOldGenCollectionUsage to pass on the submit cluster, though the old 10m works fine on my Mac. New webrev:
Thanks, the change of -Xmx and -Xms to 12m now also makes the test pass
on my workstation.
> http://cr.openjdk.java.net/~phh/8195115/webrev.03/
There seems to be some trailing whitespace in the patch, have you run
jcheck (or `hg diff` which highlights trailing whitespace in red)?
Please see
+ TraceMemoryManagerStats tms(&_memory_manager, gc_cause(),
+ collector_state()->yc_type() == Mixed
/* allMemoryPoolsAffected */);
+
^---- whitespace
and
+int MemoryManager::add_pool(MemoryPool* pool) {
+ int index = _num_pools;
^---- whitespace
Another small comment, I would have written
+void GCMemoryManager::add_pool(MemoryPool* pool) {
+ int index = MemoryManager::add_pool(pool);
+ _pool_always_affected_by_gc[index] = true;
+}
+
+void GCMemoryManager::add_pool(MemoryPool* pool, bool
always_affected_by_gc) {
+ int index = MemoryManager::add_pool(pool);
+ _pool_always_affected_by_gc[index] = always_affected_by_gc;
+}
+
as
+void GCMemoryManager::add_pool(MemoryPool* pool) {
+ add_pool(pool, true);
+}
+
+void GCMemoryManager::add_pool(MemoryPool* pool, bool
always_affected_by_gc) {
+ int index = MemoryManager::add_pool(pool);
+ _pool_always_affected_by_gc[index] = always_affected_by_gc;
+}
+
to not have to two duplicate implementations of
GCMemoryManager::add_pool. Would you mind updating the patch with this
change (and remove the trailing whitespace)?
Thanks,
Erik
> Thanks,
>
> Paul
>
> On 6/12/18, 6:52 AM, "Erik Helin" <erik.helin at oracle.com> wrote:
>
> (adding back serviceability-dev, please keep both hotspot-gc-dev and
> serviceability-dev)
>
> Hi Paul,
>
> before I start re-reviewing, did you test the new version of the patch
> via the jdk/submit repository [0]?
>
> Thanks,
> Erik
>
> [0]: http://hg.openjdk.java.net/jdk/submit
>
> On 06/09/2018 03:29 PM, Hohensee, Paul wrote:
> > Didn't seem to make it to hotspot-gc-dev...
> >
> > On 6/8/18, 10:14 AM, "serviceability-dev on behalf of Hohensee, Paul" <serviceability-dev-bounces at openjdk.java.net on behalf of hohensee at amazon.com> wrote:
> >
> > Back after a long hiatus...
> >
> > Thanks, Eric, for your review. Here's a new webrev incorporating your recommendations.
> >
> > Bug: https://bugs.openjdk.java.net/browse/JDK-8195115
> > Webrev: http://cr.openjdk.java.net/~phh/8195115/webrev.02/
> >
> > TIA for your re-review. Plus, may I have another reviewer look at it please?
> >
> > Paul
> >
> > On 2/26/18, 8:47 AM, "Erik Helin" <erik.helin at oracle.com> wrote:
> >
> > Hi Paul,
> >
> > a couple of comments on the patch:
> >
> > - memoryService.hpp:
> > + 150 bool countCollection,
> > + 151 bool allMemoryPoolsAffected = true);
> >
> > There is no need to use a default value for the parameter
> > allMemoryPoolsAffected here. Skipping the default value also allows
> > you to put allMemoryPoolsAffected to TraceMemoryManager::initialize
> > in the same relative position as for the constructor parameter (this
> > will make the code more uniform and easier to follow).
> >
> > - memoryManager.cpp
> >
> > Instead of adding a default parameter, maybe add a new method?
> > Something like GCMemoryManager::add_not_always_affected_pool()
> > (I couldn't come up with a shorter name at the moment).
> >
> > - TestMixedOldGenCollectionUsage.java
> >
> > The test is too strict about how and when collections should
> > occur. Tests written this way often become very brittle, they might
> > e.g. fail to finish a concurrent mark on time on a very slow, single
> > core, machine. It is better to either force collections by using the
> > WhiteBox API or make the test more lenient.
> >
> > Thanks,
> > Erik
> >
> > On 02/22/2018 09:54 PM, Hohensee, Paul wrote:
> > > Ping for a review please.
> > >
> > > Thanks,
> > >
> > > Paul
> > >
> > > On 2/16/18, 12:26 PM, "serviceability-dev on behalf of Hohensee, Paul" <serviceability-dev-bounces at openjdk.java.net on behalf of hohensee at amazon.com> wrote:
> > >
> > > The CSR https://bugs.openjdk.java.net/browse/JDK-8196719 for the original fix has been approved, so I’m back to requesting a code review, please.
> > >
> > > Bug: https://bugs.openjdk.java.net/browse/JDK-8195115
> > > Webrev: http://cr.openjdk.java.net/~phh/8195115/webrev.hs.01/
> > >
> > > Passed a submit repo run, passes its jtreg test, and a JDK8 version is in production use at Amazon.
> > >
> > > From the original RR:
> > >
> > > > The bug is that from the JMX point of view, G1’s incremental collector
> > > > (misnamed as the “G1 Young Generation” collector) only affects G1’s
> > > > survivor and eden spaces. In fact, mixed collections run by this
> > > > collector also affect the G1 old generation.
> > > >
> > > > This proposed fix is to record, for each of a JMX garbage collector's
> > > > memory pools, whether that memory pool is affected by all collections
> > > > using that collector. And, for each collection, record whether or not
> > > > all the collector's memory pools are affected. After each collection,
> > > > for each memory pool, if either all the collector's memory pools were
> > > > affected or the memory pool is affected for all collections, record
> > > > CollectionUsage for that pool.
> > > >
> > > > For collectors other than G1 Young Generation, all pools are recorded as
> > > > affected by all collections and every collection is recorded as
> > > > affecting all the collector’s memory pools. For the G1 Young Generation
> > > > collector, the G1 Old Gen pool is recorded as not being affected by all
> > > > collections, and non-mixed collections are recorded as not affecting all
> > > > memory pools. The result is that for non-mixed collections,
> > > > CollectionUsage is recorded after a collection only the G1 Eden Space
> > > > and G1 Survivor Space pools, while for mixed collections CollectionUsage
> > > > is recorded for G1 Old Gen as well.
> > > >
> > > > Other than the effect of the fix on G1 Old Gen MemoryPool.
> > > > CollectionUsage, the only external behavior change is that
> > > > GarbageCollectorMXBean.getMemoryPoolNames will now return 3 pool names
> > > > rather than 2.
> > > >
> > > > With this fix, a collector’s memory pools can be divided into two
> > > > disjoint subsets, one that participates in all collections and one that
> > > > doesn’t. This is a bit more general than the minimum necessary to fix
> > > > G1, but not by much. Because I expect it to apply to other incremental
> > > > region-based collectors, I went with the more general solution. I
> > > > minimized the amount of code I had to touch by using default parameters
> > > > for GCMemoryManager::add_pool and the TraceMemoryManagerStats constructors.
> > >
> > >
> > >
> >
> >
> >
> >
>
>
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