RFR: 8284950: CgroupV1 detection code should consider memory.swappiness [v2]

[Severin Gehwolf]

On Wed, 20 Apr 2022 18:18:25 GMT, xpbob <duke at openjdk.java.net> wrote:

>> set memory.swappiness to 0,swap space will not be used 
>> determine the value of memory.swappiness
>> https://www.kernel.org/doc/Documentation/cgroup-v1/memory.txt
>> 
>> 
>>     Memory Limit: 50.00M
>>     Memory Soft Limit: Unlimited
>>     Memory & Swap Limit: 100.00M
>>     Maximum Processes Limit: 4194305 
>> 
>> =>
>> 
>>     Memory Limit: 50.00M
>>     Memory Soft Limit: Unlimited
>>     Memory & Swap Limit: 50.00M
>>     Maximum Processes Limit: 4194305
>
> xpbob has updated the pull request incrementally with one additional commit since the last revision:
> 
>   add test and hotspot data

Changes requested by sgehwolf (Reviewer).

test/hotspot/jtreg/containers/docker/TestMemoryAwareness.java line 164:

> 162:             opts.addDockerOpts("--memory-swappiness", "0");
> 163:         } else {
> 164:             opts.addDockerOpts("--memory-swappiness", "60");

Unfortunately this breaks on a cgroups v2 system as `--memory-swappiness` is not supported there. I'd prefer if this wouldn't piggy back on the existing test, but actually assert that swap is properly reported as the same as the memory limit if `--memory-swappiness=0`. Also, this test only verifies the Java (core-libs) change, not the hotspot change. That would have to be done via some `TestMisc` variant which uses `print_container_info()`.

-------------

PR: https://git.openjdk.java.net/jdk/pull/8285