Re: [PATCH v2 21/23] -- DO NOT APPLY!!! -- sched/cache/stats: Add schedstat for cache aware load balancing

[Chen, Yu C]

On 12/19/2025 1:03 PM, Yangyu Chen wrote:
> > On 4 Dec 2025, at 07:07, Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx> wrote:
> >
> > From: Chen Yu <yu.c.chen@xxxxxxxxx>
> >
> > Debug patch only.
> >
> > With cache-aware load balancing enabled, statistics related to its activity
> > are exposed via /proc/schedstat and debugfs. For instance, if users want to
> > verify metrics like the number of exceeding RSS and nr_running limits, they
> > can filter the output of /sys/kernel/debug/sched/debug and compute the required
> > statistics manually:
> >
> > llc_exceed_cap SUM: 6
> > llc_exceed_nr SUM: 4531
> >
> > Furthermore, these statistics exposed in /proc/schedstats can be queried manually
> > or via perf sched stats[1] with minor modifications.
>
> Hi Tim,
>
> This patch looks great, especially for multithread Verilator workloads
> on clustered LLC (like AMD EPYC). I'm discussing with Verilator
> upstream to disable automatic userspace affinity assignment in
> Verilator if such feature exist [1]. During the discussion, I think
> there should be a way for userspace software to detect if such a
> feature exists. Could we expose it in `/proc/schedstats` to allow
> userspace software to detect such a feature? We can just use this
> patch and remove the "DO NOT APPLY" tag.

Thanks for the test Yangyu. Does /sys/kernel/debug/sched/llc_enabled
work for you?
Anyway we can try to include /proc/schedstats as the formal one
in the next version.

Thanks,
Chenyu

> [1] https://github.com/verilator/verilator/issues/6826#issuecomment-3671287551
>
> Thanks,
> Yangyu Chen

>