RFR (S): 8020155: PSR:PERF G1 not collecting old regions when humongous allocations interfer

Per Liden per.liden at oracle.com
Thu Jul 11 14:59:49 UTC 2013

Looks good.


On 2013-07-11 15:27, Bengt Rutisson wrote:
> Hi everyone,
> Could I get a couple of reviews for this small change?
> http://cr.openjdk.java.net/~brutisso/8020155/webrev.00/
> 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.
> Thanks,
> Bengt

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