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Thu, 12 Nov 2026 06:02:32 -0800 (PST) Received: from scheduler.schedules ([85.100.66.184]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4bb4e2adf53sm71538805e9.15.2026.11.12.06.02.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Nov 2026 06:02:30 -0800 (PST) Date: Thu, 12 Nov 2026 17:02:27 +0300 From: Kayra Cizmeci To: Peter Zijlstra Cc: mingo@kernel.org, linux-kernel@vger.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, joshdon@google.com, tj@kernel.org, jakub@okonski.org Subject: Re: [PATCH 2/3] sched/fair: Make cfs_rq::idle the sum of ancestor tg::idle Message-ID: References: <20261105165525.011876858@infradead.org> <20261105170157.616859418@infradead.org> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20261105170157.616859418@infradead.org> :-(. Look here: https://lore.kernel.org/oe-kbuild-all/202611121431.06YgiErz-lkp@intel.com/ On Thu, Nov 05, 2026 at 05:55:27PM +0100, Peter Zijlstra wrote: > Rather than keeping cfs_rq::idle as a copy of tg::idle, make it the sum of > all ancestor tg::idle. This makes it trivial to tell if the current cgroup > is marked idle somewhere along its ancestral path. > > This makes se_id_idle() behave differently. Notably is will now be true > when there is a idle cgroup anywhere in the ancestor path. This > addresses an issue where preemption of cgroup::idle was overlooked when > flattening the runqueue. > > Fixes: 85570f10a4c6 ("sched/eevdf: Move to a single runqueue") > Signed-off-by: Peter Zijlstra (Intel) > --- > kernel/sched/core.c | 2 - > kernel/sched/debug.c | 1 > kernel/sched/fair.c | 73 ++++++++++++++++++++++++++++++++------------------- > kernel/sched/sched.h | 4 +- > 4 files changed, 50 insertions(+), 30 deletions(-) > > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -8970,7 +8970,7 @@ void __init sched_init(void) > rq->nr_running = 0; > rq->calc_load_active = 0; > rq->calc_load_update = jiffies + LOAD_FREQ; > - init_cfs_rq(&rq->cfs); > + init_cfs_rq(&rq->cfs, NULL); > init_rt_rq(&rq->rt); > init_dl_rq(&rq->dl); > #ifdef CONFIG_FAIR_GROUP_SCHED > --- a/kernel/sched/debug.c > +++ b/kernel/sched/debug.c > @@ -1090,6 +1090,7 @@ void print_cfs_rq(struct seq_file *m, in > SEQ_printf(m, " .%-30s: %d\n", "h_nr_runnable", cfs_rq->h_nr_runnable); > SEQ_printf(m, " .%-30s: %d\n", "h_nr_queued", cfs_rq->h_nr_queued); > SEQ_printf(m, " .%-30s: %d\n", "h_nr_idle", cfs_rq->h_nr_idle); > + SEQ_printf(m, " .%-30s: %d\n", "idle", cfs_rq->idle); idle is only in the CONFIG_FAIR_GROUP_SCHED :-(. So as the robot says, this breaks compiling in !CONFIG_FAIR_GROUP_SCHED. AFAICT tho, moving this down below in CONFIG_FAIR_GROUP_SCHED next to h_load and other guys will solve the issue no? Cheers, Kayra