RFR: 8292541: [Metrics] Reported memory limit may exceed physical machine memory [v5]

[Jonathan Dowland]

On Fri, 26 Aug 2022 09:46:16 GMT, Severin Gehwolf <sgehwolf at openjdk.org> wrote:

>> Jonathan Dowland has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Add a log-line for total physical memory
>>   
>>   This is relied upon for tests in
>>   test/hotspot/jtreg/containers/docker/TestMemoryAwareness.java
>
> src/hotspot/os/linux/cgroupSubsystem_linux.cpp line 532:
> 
>> 530:   }
>> 531:   jlong phys_mem = os::Linux::physical_memory();
>> 532:   log_trace(os, container)("total physical memory: " JLONG_FORMAT, phys_mem);
> 
> This won't work reliably as expected without the change in #9880 which changes what `os::Linux::physical_memory()` reports (it's set to the container limit via `OSContainer::init()` without #9880 causing weird output). I believe this should not be integrated as-is.
> 
> 
> $ sudo podman run --rm -ti --memory 1G -v $(pwd)/./build/linux-x86_64-server-fastdebug/images/jdk:/opt/jdk:z fedora:36
> [root at 7494fe07f76b /]# /opt/jdk/bin/java -Xlog:os+container=trace -version 2>&1 | grep os,container | grep 'total physical memory'
> [0.001s][trace][os,container] total physical memory: 33258033152
> [0.063s][trace][os,container] total physical memory: 1073741824
> 
> 
> Yes, this works, because `firstMatch()` is being used, but it's an ugly hack which we should avoid.

Fair enough. You're right, it only works because the first match is prior to cgroups overwriting the physical number. I'm happy to wait until we merge #9880.

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PR: https://git.openjdk.org/jdk/pull/10017