Re: [PATCH 5.10+5.4 0/3] sched/topology: Fix missing scheduling domain levels

[Greg KH <gregkh@linuxfoundation.org>]

On Sat, Mar 05, 2022 at 09:44:27AM -0700, dann frazier wrote:
> The LTP cpuset_sched_domains test, authored by Miao Xie, fails on a Kunpeng920
> server that has 4 NUMA nodes:
>   https://launchpad.net/bugs/1951289
> 
> This does appear to be a real bug. /proc/schedstat displays 4 domain levels for
> CPUs on 2 of the nodes, but only 3 levels for the others 2 (see below).
> I assume this means the scheduler is making suboptimal decisions about
> where to place/move processes. I'm not sure how to demonstrate that - but
> open to suggestions if that evidence is important justification for stable.
> 
> This is not a problem in current upstream kernels, so I bisected and found
> that the first patch here fixes it. I can't tell from the commit message
> if fixing this case was Valentin's intent, or just a happy side-effect of the
> set conversion. The other two patches fix regressions introduced by the first.
> All cherry-pick cleanly back to 5.10.y and 5.4.y. This platform easily
> reproduces the problem Dietmar's fix addresses. I don't have hardware to test
> the ia64 fix.
> 
> Note: This also impacts earlier stable trees, but require some minor porting,
> so I'll submit fixes for those separately.
> 
> Here's a comparison of /proc/schedstat before & after applying these
> fixes:

Thanks, now queued up.

greg k-h