JDK-8027132: Print deprecation warning message for the flags controlling the CMS foreground collector

[Srinivas Ramakrishna]

+1.

yes, it would be good to get rid of the extra code in the future.

reviewed webrev.
-- ramki


On Thu, Oct 24, 2013 at 8:00 AM, Erik Helin <erik.helin at oracle.com> wrote:

> Bengt,
>
> looks even better :)
>
> Thanks,
> Erik
>
> On 2013-10-24, Bengt Rutisson wrote:
> >
> > Thanks for the reviews Erik and Stefan!
> >
> > Thomas suggested to add a JTreg test for these flags. Here is a
> > webrev with the same code change as before but with a test added:
> >
> > http://cr.openjdk.java.net/~brutisso/8027132/webrev.01/
> >
> > Thanks, Thomas for pointing this out.
> >
> > Bengt
> >
> >
> > On 2013-10-24 14:26, Erik Helin wrote:
> > >Hi Bengt,
> > >
> > >looks good, thanks for doing this!
> > >
> > >Erik
> > >
> > >On 2013-10-24, Bengt Rutisson wrote:
> > >>Hi all,
> > >>
> > >>Can I have a couple of reviews for this small change?
> > >>
> > >>http://cr.openjdk.java.net/~brutisso/8027132/webrev.00/
> > >>
> > >>CR: https://bugs.openjdk.java.net/browse/JDK-8027132
> > >>
> > >>Background from the CR:
> > >>
> > >>Normally CMS reverts to the SerialOld GC when it needs to do a full
> > >>GC. There is a mode in CMS to instead use the "foreground
> > >>collector".  This is a single threaded stop-the-world mode which
> > >>completes an ongoing concurrent CMS collection (a normal
> > >>"background" collection in CMS).
> > >>
> > >>The foreground collector is very slow and to enable it two flags are
> > >>required. First -XX:-UseCMSCompactAtFullCollection needs to be added
> > >>to the command line to turn off the SerialOld collector, then
> > >>-XX:CMSFullGCsBeforeCompaction needs to be set to a value greater
> > >>than 0.
> > >>
> > >>The foreground collector adds a lot of complexity to the CMS code
> > >>but has few (if any?) use cases. Thus, it would be good to remove it
> > >>to simplify the code. In order to remove it we need to deprecate it
> > >>first. This bug report is only about deprecating the flags to allow
> > >>us to remove the foreground collector in a future release.
> > >>
> > >>The following flags should log a warning message that they are
> > >>deprecated, but the VM should still continue to work when they are
> > >>used:
> > >>
> > >>UseCMSCompactAtFullCollection
> > >>CMSFullGCsBeforeCompaction
> > >>UseCMSCollectionPassing
> > >>
> > >>Thanks,
> > >>Bengt
> >
>
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