RFR: 8327946: containers/docker/TestJFREvents.java fails when host kernel config vm.swappiness=0 after JDK-8325139 [v3]

[Severin Gehwolf]

On Fri, 12 Apr 2024 08:28:54 GMT, SendaoYan <syan at openjdk.org> wrote:

>> Hi,
>> 
>> According to the [docker document](https://docs.docker.com/config/containers/resource_constraints/#--memory-swappiness-details), the default value of --memory-swappiness is inherited from the host machine. So, when the the kernel config vm.swappiness=0 on the host machine, this testcase will fail, because of docker container can not use swap memory, the deafult value of --memory-swappiness is 0.
>> 
>> When the host kernel config "vm.swappiness = 0", In order to run this testcase passed , there are three methods:
>> 
>> 1. change `.shouldContain("totalSize = " + expectedTotalValue)` to `.shouldContain("totalSize = "`, which ignored the `expectedTotalValue`, because the `expectedTotalValue` could be 0(swap memroy is disable when --memory-swappiness=0) or could be 104857600(300MB-200MB=100MB), it depends on the host machine config `vm.swappiness`
>> 2. Change the default `--memory-swappiness` 0 to non-zero, such as 60.
>> 3. Change the host kernel config `vm.swappiness=0` to `vm.swappiness=60`. I think it's not a good idea.
>> 
>> Maybe the 2rd method seems more resonable.
>> 
>> 
>> Thanks,
>> -sendao
>
> SendaoYan has updated the pull request incrementally with one additional commit since the last revision:
> 
>   If isCgroupV1() return true, add docker run opts --memory-swappiness=60

I don't think we need `Whitebox`. A simpler check would be to use the `Metrics` class. See for example `test/hotspot/jtreg/containers/docker/TestMemoryWithCgroupV1.java`.

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PR Review: https://git.openjdk.org/jdk/pull/18225#pullrequestreview-1996282528