[jdk16] RFR: 8259765: ZGC: Handle incorrect processor id reported by the operating system [v2]

[David Holmes]

On 22/01/2021 9:21 pm, Per Liden wrote:
> On Sat, 16 Jan 2021 13:00:04 GMT, David Holmes <dholmes at openjdk.org> wrote:
> 
>>> Per Liden has updated the pull request incrementally with one additional commit since the last revision:
>>>
>>>    Review
>>
>> So we have to penalize all correctly functioning users because of one broken environment? Can we not detect this broken environment at startup and inject a workaround then?
>>
>> Why is this an environment that is important enough that OpenJDK has to make changes to deal with a broken environment?
>>
>> Cheers,
>> David
> 
> @dholmes-ora Do you still have questions or concerns here, or can I go ahead and integrate this?

I remain concerned about the justification for putting in this 
workaround for a broken virtualization system. I would be happier if the 
bug was acknowledged and a fix was in the pipeline so we would know how 
long we have to carry this for.

> I've gone through all uses of sysconf(_SC_NPROCESSORS_*) and sched_getaffinity() we have, and they look fine. I've also looked at how the OSContainer stuff behaves in this environment, and it also looks fine. In summary, the only problem I can spot is related to sched_getcpu().

So IIUC what we suspect is that sched_getcpu is reporting physical id's 
rather than virtualized ones. I find it hard to imagine how only one API 
in this area can be affected by such a bug, but if that appears to be 
the case then that is reassuring.

I won't "block" this, but I'm not happy about it.

Thanks,
David

> -------------
> 
> PR: https://git.openjdk.java.net/jdk16/pull/124
>