On Mon, 1 Feb 2021 06:16:34 GMT, Lin Zang <lz...@openjdk.org> wrote: >>> I think if you can avoid the 4th argument by just enabling parallel by >>> default sounds like a good idea. Is there any reason not to use parallel >>> heap dump? Also, I'm not familiar with the terms "compression backends" and >>> "active workers". Can you explain them. >> >> For parallel heap dump, I think expose the "parallel" option is useful when >> user want to control the number of threads that works on parallel dumping. >> One reason is to control the CPU load to not affect too much on other >> processes on system. >> >> The "active workers" is the value that returned by gang->active_workers(). >> And I think "active workers" is the number of available threads that could >> be used for parallally working on something. my understanding is that this >> value could be dynamically changed at runtime, but it is limited by the JVM >> option "-XX:ParallelGCThreads". >> >> The "compression backend" is introduced by "gz=" option, it is actually a >> "backend" that write heap dump data to file, and if there is compression >> level specified, the "backend" will do compression first and then write to >> file. The whole "backend" works parallelly, before this PR, the backend >> thread number is dicided by "active workers". >> >> With this PR, the relation of parallel heap iteration threads (parallel >> dumper), the file writing threads (compression backend) and the >> "active_works" is like following: >> num_of_dumper_threads + num_of_compression_backend = >> active_workers. >> >> BRs, >> Lin > > Hi All, > As discussed in this PR, it is reasonable to enable parallel heap dump by > default rather than introducing a new "parallel" option. I would like to > close the CSR at https://bugs.openjdk.java.net/browse/JDK-8260424.
Dear All, I have updated the patch and remove the introduction of new "parallel" option. So there can be no backward-compatibility issue for jmap -dump command. May I ask your help to remove the CSR label if agreed? BRs, Lin ------------- PR: https://git.openjdk.java.net/jdk/pull/2261
