On Fri, 29 Jan 2021 00:36:54 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. > >> 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. ------------- PR: https://git.openjdk.java.net/jdk/pull/2261
