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

[Bengt Rutisson]

Thanks for looking at this, Ramki!

Bengt

On 2013-10-25 20:14, Srinivas Ramakrishna wrote:
> +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 
> <mailto: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/
>     <http://cr.openjdk.java.net/%7Ebrutisso/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/
>     <http://cr.openjdk.java.net/%7Ebrutisso/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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