On Fri, 10 Nov 2023 09:13:06 GMT, Long Yang <d...@openjdk.org> wrote:
> I would like to fix this. > > Create 4096 threads, and the stack depth of each thread is 256. > After running jmx.dumpAllThreads(true, true), the RSS reaches 5.3GiB. > After optimization, the RSS is 250MiB. > > I would appreciate it if anyone could review this. > > --------- > update > > If the number of `threads` and `stack depth` are relatively large, we need to > apply for more space in `ResourceArea` during the execution of > `jmx.dumpAllThreads(true, true)`. > > The reason is that `VM_ThreadDump::doit` creates `vframe` for each `frame` of > each `thread`. > https://github.com/openjdk/jdk/blob/fe0ccdf5f8a5559a608d2e2cd2b6aecbe245c5ec/src/hotspot/share/services/threadService.cpp#L704 > sizeof `vframe` is 4808 (bytes), and sizeof `compiledVFrame` is 4824 (bytes), > mainly because the `xmm registers` in `RegisterMap` are relatively large. > Assuming there are 4096 `threads` and each `thread` has 256 `frames`, the > memory required is 4096 * 256 * 4824 = 4.7GiB。 > > These memories of all threads are released once by the the initial > `ResourceMark` of `VM_ThreadDump::doit`. > https://github.com/openjdk/jdk/blob/fe0ccdf5f8a5559a608d2e2cd2b6aecbe245c5ec/src/hotspot/share/runtime/vmOperations.cpp#L269 > My solution is to add a `ResourceMark` for each thread. This pull request has now been integrated. Changeset: 8ec6b8de Author: yibo.yl <yibo...@alibaba-inc.com> Committer: Denghui Dong <dd...@openjdk.org> URL: https://git.openjdk.org/jdk/commit/8ec6b8de3bb3d7aeebdcb45d761b18cce3bab75e Stats: 3 lines in 2 files changed: 0 ins; 2 del; 1 mod 8319876: Reduce memory consumption of VM_ThreadDump::doit Reviewed-by: dholmes, stefank ------------- PR: https://git.openjdk.org/jdk/pull/16598
