RFR (S): 8233301: Implementation of JEP 366: Deprecate the ParallelScavenge + SerialOld GC Combination
per.liden at oracle.com
Tue Nov 5 08:26:07 UTC 2019
On 11/4/19 11:46 AM, Thomas Schatzl wrote:
> On 01.11.19 00:05, Bernd Eckenfels wrote:
>> The help message:
>> Use the Parallel Old garbage collector. Deprecated.
> product(bool, UseParallelOldGC, false, \
> "Use the Serial Old garbage collection algorithm for old " \
> "generation. Deprecated." \
I know it's not easy to get this right, but I think the above might
perhaps be even more confusing. How about something like:
UseParallelGC -> "Use the Parallel garbage collector"
UseParallelOldGC -> "Use the Parallel or the Serial garbage collector
when collecting the old generation (Deprecated)."
>> Looks a bit missleading to me. I know it means the option is
>> deprecated (especially the non default negative value
> > but it could easily be understood as ParallelOld beeing deprecated.
> I hope the new text is better understandable and does not lead to the
> confusion you suggested.
> Note that the default value of "false" is correct although maybe
> surprising, as this change does not modify it. It's only that
> -XX:+UseParallelGC is actually a shorthand for "-XX:+UseParallelGC
> -XX:+UseParallelOldGC" for like forever.
> I do not want to change this here.
> Note that these strings are not the official documentation, but the
> manpage. They read:
> : Enables the use of the parallel scavenge garbage collector (also
> known as
> the throughput collector) to improve the performance of your
> application by
> leveraging multiple processors.
> By default, this option is disabled and the default collector is used.
> If it's enabled, then the `-XX:+UseParallelOldGC` option is
> automatically enabled, unless you explicitly disable it.
> and (with this change, as part of the "Deprecated" section):
> : Enables the use of the parallel garbage collector for full GCs. By
> this option is disabled. Enabling it automatically enables the
> `-XX:+UseParallelGC` option.
> Which seems in line with what is now told in the sources too.
>> There is no jtreg for +UseParallelOld. It would need to document that
>> deprecation warning is expected for that as well?
> There is a separate test case in
> test/hotspot/jtreg/runtime/CommandLine/VMDeprecatedOptions.java which
> does not seem updated for any and all deprecated options. I added this
> flag to it anyway.
> local compilation + local jtreg test
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