OperatingSystemImpl should factor cpu shares when calculating system load

[David Holmes]

On 4/05/2021 9:07 am, Argha C wrote:
> Hello David,
> It does look quite similar.
> The crux is factoring in the sum of cpu time across all shares, instead 
> of a single cpu share.
> My proposal for implementing the fix is slightly different from the PR, 
> but happy to trust your advice on taking this forward.

I would suggest liaising with the contributors of

https://github.com/openjdk/jdk/pull/3656

so see if all of the issues can be addressed together.

Cheers,
David

> 
> On Mon, May 3, 2021 at 3:21 PM David Holmes <david.holmes at oracle.com 
> <mailto:david.holmes at oracle.com>> wrote:
> 
>     Hi,
> 
>     Is this related to the issue reported here:
> 
>     https://bugs.openjdk.java.net/browse/JDK-8265836
>     <https://bugs.openjdk.java.net/browse/JDK-8265836>
> 
>     Cheers,
>     David
> 
>     On 4/05/2021 3:14 am, Argha C wrote:
>      > Hello,
>      > I wanted to report an issue we're seeing with the load
>     calculation, when
>      > running with cpu shares > 1, in a container environment.
>     Specifically,
>      > the implementation of /OperatingSystemImpl#getCpuLoad./
>      > /
>      > /
>      > /Problem/
>      > /
>      > /
>      > When running with allocation of multiple cpu shares, ie. > 1
>     unit, the
>      > load numbers do not comply with the expected range of 0-1. In the
>      > example screenshot, it goes beyond 4.
>      > This miscalculation throws off load based system heuristics, when
>      > running in a container based environment.
>      >
>      > /Proposed solution/
>      > /
>      > /
>      > In a container aware environment, for load average calculation, the
>      > number of cpu cycles, ie. /getCpuPeriod /must be multiplied by the
>      > number of requested cpu shares by the process, ie. /getCpuShares./
>      > This would ensure that the load calculation uses the correct
>     denominator
>      > for elapsed time slice periods.
>      >
>      > In the screenshot below, this would mean using /getCpuShares /as a
>      > multiplier for /periodLength./
>      >
>      > Please consider validating this behavior. I'd be happy to submit
>     a PR
>      > but I'm not an openjdk author/contributor.
>      > Thanks for your consideration.
>