Re: [PATCH v2 2/2] sched/fair: Randomize equally shallow slow-path candidates

[Peter Zijlstra]

On Thu, Sep 17, 2026 at 06:06:42PM +0200, Vincent Guittot wrote:
> On Thu, 17 Sept 2026 at 17:41, Christian Loehle
> <christian.loehle@xxxxxxx> wrote:
> >
> > Picking the first eligible idle CPU leaves a scan-order bias. Concurrent
> > slow-path selectors can choose the same CPU before either task is enqueued.
> >
> > Use reservoir sampling for equal exit latencies, resetting the candidate
> > count when a shallower candidate appears. Use the per-CPU scheduler PRNG
> > and reciprocal_scale() to avoid variable division or a second scan.
> >
> > Use a u64 latency key with U64_MAX for unpublished states. Published
> > states take precedence; when none are found, sample among the idle CPUs
> > without a published state.
> >
> > Signed-off-by: Christian Loehle <christian.loehle@xxxxxxx>
> 
> Reviewed-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>

Thanks, let me go queue this.