RFR: 8284950: CgroupV1 detection code should consider memory.swappiness [v12]

[Severin Gehwolf]

On Tue, 3 May 2022 09:21:11 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:
> 
>   remove no use copy

To be honest, the original test change was closer to what I was expecting to see. Could you clarify why we'd need to use `cgcreate` et.al. for this test? As far as I'm aware `--memory-swappiness` should work just as well.

src/hotspot/os/linux/cgroupV1Subsystem_linux.cpp line 150:

> 148:     GET_CONTAINER_INFO(julong, _memory->controller(), "/memory.swappiness",
> 149:                        "Swappiness is: " JULONG_FORMAT, JULONG_FORMAT, swappiness);
> 150:     if(swappiness == 0) {

Style: Space before `(`

src/hotspot/os/linux/cgroupV1Subsystem_linux.cpp line 152:

> 150:     if(swappiness == 0) {
> 151:       jlong memlimit = read_memory_limit_in_bytes();
> 152:       log_trace(os, container)("Memory and Swap Limit has been reset to " JULONG_FORMAT " because of Swappiness is 0", memlimit);

`s/because of Swappiness is 0/because swappiness is 0/g`

test/hotspot/jtreg/containers/docker/TestCgroupV1Memory.java line 58:

> 56:             try {
> 57:                 testMemoryLimit();
> 58:                 testMemoryLimitWithSwappiness();

Only `testMemoryLimitWithSwappiness()` should be `cgroupv1` conditional.

test/lib/jdk/test/lib/containers/cgroup/CgroupV1TestUtils.java line 34:

> 32: 
> 33: 
> 34: public class CgroupV1TestUtils {

I'm not sure what the point of this class is. Wouldn't we be able to test the same thing with the existing docker infrastructure using `--memory-swappiness=0` as docker option? As far as I can see this utility adds a dependency in `libcgroup` and related tools, which isn't necessarily installed on test systems. Docker dep, on the other hand, is enforced via `@require` tag.

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

Changes requested by sgehwolf (Reviewer).

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