Hi David, > However I'm not clear how this solves the problem of destroying > the monitor while it can still be being accessed - is the dumping > occurring at a safepoint in the WorkGang threads?
Because when the run_task() method returns, I can be sure none of the work gang threads still use the mutex. They have to exit the thread_loop() method to finish the task. And by exiting the method they have released the mutex. Best regards, Ralf From: David Holmes <david.hol...@oracle.com> Sent: Wednesday, March 18, 2020 6:11 AM To: Schmelter, Ralf <ralf.schmel...@sap.com>; Ioi Lam <ioi....@oracle.com>; Langer, Christoph <christoph.lan...@sap.com>; Yasumasa Suenaga <suen...@oss.nttdata.com>; serguei.spit...@oracle.com <serguei.spit...@oracle.com>; hotspot-runtime-...@openjdk.java.net runtime <hotspot-runtime-...@openjdk.java.net> Cc: serviceability-dev@openjdk.java.net <serviceability-dev@openjdk.java.net> Subject: Re: RFR(L) 8237354: Add option to jcmd to write a gzipped heap dump Hi Ralf, On 13/03/2020 9:43 pm, Schmelter, Ralf wrote: > Hi, > > I have updated the webrev: http://cr.openjdk.java.net/~rschmelter/webrevs/8237354/webrev.1/ > > It has the following significant changes: > > - The jcmd now uses two separate flags. The -gz flag is now a boolean flag > which toggles the compression on/off. And the new -gz-level flag can be used > to change the compression level. If tried to change the jlong flag coding to > allow the old behavior (only one flag, which acts both as a boolean flag and a jlong flag), but decided against it, since it changes the semantic of a jlong flag. And I don't expect the -gz-level flag to be used all that much. > > - I no longer use my own threads. Instead I use the WorkGang returned from > CollectedHeap:: get_safepoint_workers(). This works fine, apart from > Shenandoah GC, which runs into assertions when calling the > CollectedHeap::object_iterate() method from a worker thread. I'm not sure if the assertion is too strong, but since the GC is currently experimental, I switch back to single threading in this case (as would be the case for serial GC or epsilon GC). Using the worker threads removes the problems the original code had regarding destruction of the monitor used. I'm glad to see you are no longer using your own threads, and I apologise that I have not yet been able to look further into the thread lifecycle issues you encountered. However I'm not clear how this solves the problem of destroying the monitor while it can still be being accessed - is the dumping occurring at a safepoint in the WorkGang threads? Thanks, David -----
