RFR (S): JDK-8077841: G1: Remove PrintReachable support

Bengt Rutisson bengt.rutisson at oracle.com
Thu Apr 16 07:21:17 UTC 2015

On 2015-04-16 09:18, Thomas Schatzl wrote:
> Hi,
> On Wed, 2015-04-15 at 13:52 +0200, Bengt Rutisson wrote:
>> Hi everyone,
>> Could I have a couple of reviews for this change to remove the
>> PrintReachable support in G1?
>> https://bugs.openjdk.java.net/browse/JDK-8077841
>> http://cr.openjdk.java.net/~brutisso/8077841/webrev.00/
>> There are three develop flags that allow G1 to dump all objects on the
>> heap to a text format:
>> G1PrintReachableAtInitialMark
>> G1VerifyDuringGCPrintReachable
>> G1PrintReachableBaseFile
>> Turning on this dumping code will dump all objects in all regions to the
>> file specified by G1PrintReachableBaseFile,
>> Several things are disturbing with this code:
>> - The way the code opens a separate file and writes to it is pretty
>> uncommon for our logging code
>> - The flags are develop flags, so not usable in product code - even
>> druring verification
>> - The format the heap is dumped in is not a standard format so there is
>> no tool support for it
>> - There is already standard ways of dumping the heap, using hprof for
>> example.
>> - It is pretty unclear when the information logged by PrintReachable is
>> useful.
>> I've asked around a bit and as far as I can tell no one has been using
>> this feature for a long time. So, rather than trying to fix the code I
>> propose that we remove it.
>    looks good pending StefanK's comments.

Thanks, Thomas. I've fixed StefanK's comment and am pushing this now.


> Thanks,
>    Thomas

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