On Mon, 2020-07-27 at 11:52 -0400, Bob Vandette wrote: > > On Jul 27, 2020, at 11:32 AM, Severin Gehwolf <sgehw...@redhat.com> wrote: > > > > Hi Bob, > > > > On Fri, 2020-07-24 at 15:21 -0400, Bob Vandette wrote: > > > I’ve been monitoring the discussion on your jdk8u alias and I can’t help > > > wondering if > > > my original decision to provide two different implementations of this > > > container detection > > > logic was the best way to go. > > > > > > I didn’t want to have an all Java implementation since the VM needs to > > > initialize it’s > > > memory and cpu sizing very early on prior to its ability to run Java code. > > > > > > If we put all of the logic in the VM, then we’d end up with a pretty wide > > > interface to > > > the VM and more overhead extracting values (due to JNI) although the Java > > > logic > > > typically ends up in native code anyway. Having the functionality in the > > > VM > > > makes it easier to add JFR events. Having a pure Java implementation > > > makes it > > > easier to support the OS MBeans. The maintenance of supporting both > > > implementations > > > is a bit of a pain. > > > > Add to that that Java metrics return non-null for any controller it > > finds. The JVM doesn't. Container support is turned on there only if > > all cpu and memory controllers are found. > > That was intentional. I wanted the VM to configure itself consistently. > Either all needed value are present or revert to non container mode. > For Metrics, I felt it was ok to report whatever is available.
Yes, I know. Thanks. What I meant to say was that it's another consideration to take into account if at some point a JVM-only-impl + Java wrapper approach would be taken. Thanks, Severin > > > > > Assuming no one has the time or desire to migrate the logic to > > > the VM and provide > > > Java wrapper logic, I’m ok with what you are proposing. It’s one > > > step on the path. > > > The VM support and the Java level support are really for two > > > different consumers > > > but I think it would be cleaner and less confusing to disable > > > both on one flag rather > > > than support two options. > > > > OK, agreed. I've filed: > > https://bugs.openjdk.java.net/browse/JDK-8250627 > > > > Thanks, > > Severin > > > > > Bob. > > > > > > > On Jul 24, 2020, at 12:13 PM, Severin Gehwolf < > > > > sgehw...@redhat.com> > > > > wrote: > > > > > > > > Hi, > > > > > > > > For hotspot one can disable container detection with a simple > > > > switch: > > > > > > > > $ java -XX:-UseContainerSupport -Xlog:os+container=trace > > > > -version > > > > [0.000s][trace][os,container] OSContainer::init: Initializing > > > > Container Support > > > > [0.000s][trace][os,container] Container Support not enabled > > > > openjdk version "15-internal" 2020-09-15 > > > > OpenJDK Runtime Environment (build 15-internal+0- > > > > adhoc.sgehwolf.openjdk-head-2) > > > > OpenJDK 64-Bit Server VM (build 15-internal+0- > > > > adhoc.sgehwolf.openjdk-head-2, mixed mode, sharing) > > > > > > > > The same cannot be achieved with the Java code, > > > > jdk.internal.platform.Metrics.java and friends in the JDK. At > > > > the > > > > time > > > > Metrics were added the only consumer of them was the Java > > > > Launcher > > > > via > > > > -XshowSettings:system. This has changed with JDK-8226575: > > > > OperatingSystemMXBean should be made container aware. > > > > > > > > It is known that in certain cases the container detection code > > > > will > > > > detect for a system to be supposedly in a container where it > > > > actually > > > > isn't: > > > > https://bugs.openjdk.java.net/browse/JDK-8227006?focusedCommentId=14275604&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14275604 > > > > > > > > For hotspot there is a flag, to turn auto-detection off for > > > > exactly > > > > the > > > > case when heuristics are wrong: -XX:-UseContainerSupport. > > > > However, > > > > this > > > > flag has no effect on the Java metrics code. There is a risk > > > > that > > > > on > > > > some systems the auto-detection will be wrong and might cause > > > > regressions. > > > > > > > > I propose to make the Java metrics code adhere to -XX:+/- > > > > UseContainerSupport flag. Do you think this would be useful? If > > > > yes, > > > > I'll file a bug and propose a patch for it. > > > > > > > > Thoughts? Opinions? > > > > > > > > Thanks, > > > > Severin > > > >
