[crac] RFR: 8328344: [CRaC] Avoid error when running with -XX:+PerfDisableSharedMem [v4]

[Anton Kozlov]

On Fri, 22 Mar 2024 13:59:54 GMT, Volker Simonis <simonis at openjdk.org> wrote:

>> CRaC tries to unconditionally restore the hsperf file, even if the checkpointed JVM process was started with `-XX:+PerfDisableSharedMem`.
>> 
>> The fix is trivial: check for the existence of the hsperf file in `PerfMemoryLinux::restore()` just as we already do it in `PerfMemoryLinux::checkpoint()`.
>
> Volker Simonis has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Don't wait 2x10 seconds when with -XX:+PerfDisableSharedMem

test/jdk/jdk/crac/PerfMemoryRestoreTest.java line 68:

> 66:         Path perfdata = Path.of("/tmp", "hsperfdata_" + System.getProperty("user.name"), pid);
> 67:         if (perfDisableSharedMem) {
> 68:             Thread.sleep(100);

I like the refactoring and that we can control this delay independently. 

Nit-picking: should not be this a named constant? And does 100ms has any reason behind, or can it be 1sec (a little bit safer)?

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PR Review Comment: https://git.openjdk.org/crac/pull/153#discussion_r1535880319