On 12/04/2018 11:33 PM, Magnus Ihse Bursie wrote:
On 2018-04-12 14:15, David Holmes wrote:
Hi Magnus,
On 12/04/2018 9:39 PM, Magnus Ihse Bursie wrote:
It is currently easy to add new JVM features to the JVM build, but it
is not possible to remove features.
With this change, features can be both added or removed from the
default set. They are added using --with-jvm-features=f1,f2 and
removed using --with-jvm-features=-f1,-f2. The syntax can be
combined, so --with-jvm-features=dtrace,-nmt will enable dtrace but
disable native memory tracking.
I need to point out that we have never tested disabling individual VM
features likes this. They are either all on, or all off for the
minimal VM! There may be implicit dependencies between features.
Well, I have. :-) However, I don't do that regularly, and changes might
very well have crept in. As always, if you build something non-standard
that is not regularly tested, you're on your own.
Feels to me like you've taken away the safety-fence and are encouraging
people to attempt these unsupported configurations. Whether that was
your intent or not.
In any case, the purpose of this is not so much to disable existing JVM
features (after all, no one has really been missing this functionality),
as to pave the way for the upcoming patch for including/excluding
individual GCs.
Surely a GC selection flag would have sufficed.
David
/Magnus
David
I also included some additional code cleanup and fixes, such as
printing the JVM feature set at the summary.
Bug: https://bugs.openjdk.java.net/browse/JDK-8201483
WebRev:
http://cr.openjdk.java.net/~ihse/JDK-8201483-disable-JVM-features/webrev.01
