RFR (S): 8020155: PSR:PERF G1 not collecting old regions when humongous allocations interfer
thomas.schatzl at oracle.com
Thu Jul 11 14:10:41 UTC 2013
On Thu, 2013-07-11 at 15:27 +0200, Bengt Rutisson wrote:
> Hi everyone,
> Could I get a couple of reviews for this small change?
> When the marking phase finishes we signal that we should start doing
> mixed collections by setting _last_young_gc=true. The next GC will be a
> normal young GC but after that we will start doing mixed GCs.
> G1CollectorPolicy::need_to_start_conc_mark() will return false if a
> marking cycle is already in progress or if we are doing mixed GCs. But
> it did not check the intermediate state represented by _last_young_gc.
> Instead this was explicitly checked by
> G1CollectorPolicy::record_collection_pause_end() for young GCs. However,
> need_to_start_conc_mark() is also used by humongous object allocations
> in two places. So, if a humongous allocation happens after marking has
> finished but before the following young GC has happened, we might
> trigger a new marking cycle and skip the mixed GCs.
> The fix is to move the check of _last_young_gc in to
> need_to_start_conc_mark() to make sure that we don't skip mixed GCs.
More information about the hotspot-gc-dev