On Thu, 18 Jan 2024 16:19:38 GMT, Chris Plummer <cjplum...@openjdk.org> wrote:
>> I noticed that "clhsdb jstack" seemed to hang when I attached to process >> with a somewhat large heap. It had taken over 10 minutes when I finally >> decided to have a look at the SA process (using bin/jstack), which came up >> with the following in the stack: >> >> >> at >> sun.jvm.hotspot.oops.ObjectHeap.iterateObjectsOfKlass([jdk.hotspot.agent@23-internal](jdk.hotspot.agent@23-internal)/ObjectHeap.java:117) >> at >> sun.jvm.hotspot.runtime.ConcurrentLocksPrinter.fillLocks([jdk.hotspot.agent@23-internal](jdk.hotspot.agent@23-internal)/ConcurrentLocksPrinter.java:70) >> at >> sun.jvm.hotspot.runtime.ConcurrentLocksPrinter.<init>([jdk.hotspot.agent@23-internal](jdk.hotspot.agent@23-internal)/ConcurrentLocksPrinter.java:36) >> at >> sun.jvm.hotspot.tools.StackTrace.run([jdk.hotspot.agent@23-internal](jdk.hotspot.agent@23-internal)/StackTrace.java:71) >> >> >> This code is meant to print information about j.u.c. locks. It it works by >> searching the entire java heap for instances of AbstractOwnableSynchronizer. >> This is a very expensive operation because it means not only does SA need to >> read in the entire java heap, but it needs to create a Klass mirror for >> every heap object so it can determine its type. >> >> Our testing doesn't seem to run into this slowness problem because "clhsdb >> jstack" only iterates over the heap if AbstractOwnableSynchronizer has been >> loaded, which it won't be if no j.u.c. locks have been created. This seems >> to be the case wherever we use "clhsdb jstack" in testing. We do have some >> tests that likely result in j.u.c locks, but they all use "jhsdb jstack", >> which doesn't have this issue (it requires use of the --locks argument to >> enable printing of j.u.c locks). >> >> This issue was already called out in >> [JDK-8262098](https://bugs.openjdk.org/browse/JDK-8262098). For this CR I am >> proposing that "clhsdb jstack" not include j.u.c lock scanning by default, >> and add the -l argument to enable it. This will make it similar to >> bin/jstack, which also has a -l argument, and to "clhsdb jstack", which has >> a --locks argument (which maps internally to the Jstack.java -l argument). >> >> The same changes are also being made to "clhsdb pstack". >> >> Tested with all tier1, tier2, and tier5 svc tests. > > Chris Plummer has updated the pull request incrementally with two additional > commits since the last revision: > > - update clhsdb docs > - update clhsdb docs test/hotspot/jtreg/serviceability/sa/ClhsdbJstackWithConcurrentLock.java line 67: > 65: String[] words = line.split(key + "|[, ]"); > 66: for (String word : words) { > 67: word = word.replace("<","").replace(">",""); Suggestion: word = word.replace("<", "").replace(">", ""); ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/17479#discussion_r1468628161
