From: Peter Zijlstra <peterz@infradead.org>
To: Tejun Heo <tj@kernel.org>
Cc: mingo@kernel.org, juri.lelli@redhat.com,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
vschneid@redhat.com, kprateek.nayak@amd.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/7] sched/core: Simplify/fix time updates
Date: Wed, 2 Sep 2026 16:32:09 +0200 [thread overview]
Message-ID: <20260902143209.GC687043@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <ape2abNdAgRCfEtg@slm.duckdns.org>
On Tue, Sep 01, 2026 at 07:38:49PM -1000, Tejun Heo wrote:
> Hello,
>
> On Fri, Aug 28, 2026 at 12:17:01PM +0200, Peter Zijlstra wrote:
> > +static void opt_update_rq_clock(struct rq *rq)
> > +{
> > + if (!(rq->clock_update_flags & RQCF_UPDATED))
> > + update_rq_clock(rq);
> > +}
>
> Yeah, I think this really needs sth like this. That said,
>
> > @@ -6336,18 +6336,12 @@ pick_next_task(struct rq *rq, struct rq_
> > * pick_next_task(). If the current cpu is not the core,
> > * the core may also have been updated above.
> > */
> > - if (i != cpu && (rq_i != rq->core || !core_clock_updated))
> > - update_rq_clock(rq_i);
> > + opt_update_rq_clock(rq_i);
>
> I don't think this is correct. A sibling rq wouldn't necessarily have
> RCQF_UPDATED cleared from whenever it scheduled / ticked the last time, so
> the following pick_task() can run with pretty stale rq clock.
Ah, indeed. We should clear clock_update_flags on unlock, rather than on
lock. Thanks!
next prev parent reply other threads:[~2026-09-02 14:32 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-28 10:16 [PATCH 0/7] sched: core-sched fixes and balancing Peter Zijlstra
2026-08-28 10:17 ` [PATCH 1/7] sched/core: Fix pick_next_task() self recursion Peter Zijlstra
2026-09-03 11:13 ` Aaron Lu
2026-08-28 10:17 ` [PATCH 2/7] sched/core: Simplify/fix time updates Peter Zijlstra
2026-09-02 5:38 ` Tejun Heo
2026-09-02 14:32 ` Peter Zijlstra [this message]
2026-08-28 10:17 ` [PATCH 3/7] sched/core: Allow newidle for core-sched Peter Zijlstra
2026-08-28 10:17 ` [PATCH 4/7] sched/rt: Add early exit on balance path Peter Zijlstra
2026-08-28 10:17 ` [PATCH 5/7] sched/fair: Reflow pick_task_fair() / newidle Peter Zijlstra
2026-08-28 10:17 ` [PATCH 6/7] sched/fair: Push sched_balance_newidle() unlock down Peter Zijlstra
2026-08-28 10:17 ` [PATCH 7/7] sched: Remove sched_class::balance() Peter Zijlstra
2026-09-01 23:47 ` Tejun Heo
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