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([2601:188:ca00:a00:f844:fad5:7984:7bd7]) by smtp.gmail.com with ESMTPSA id 8926c6da1cb9f-4de787f9cd1sm2841953173.140.2024.11.13.08.00.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 13 Nov 2024 08:00:39 -0800 (PST) From: Waiman Long X-Google-Original-From: Waiman Long Message-ID: <4a388ba7-8533-4c86-9135-883451f65065@redhat.com> Date: Wed, 13 Nov 2024 11:00:35 -0500 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] sched/deadline: Restore dl_server bandwidth on non-destructive root domain changes To: Juri Lelli , Tejun Heo , Johannes Weiner , Michal Koutny , Ingo Molnar , Peter Zijlstra , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider Cc: Qais Yousef , Sebastian Andrzej Siewior , "Joel Fernandes (Google)" , Suleiman Souhlal , Aashish Sharma , Shin Kawamura , Vineeth Remanan Pillai , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org References: <20241113125724.450249-1-juri.lelli@redhat.com> <20241113125724.450249-2-juri.lelli@redhat.com> Content-Language: en-US In-Reply-To: <20241113125724.450249-2-juri.lelli@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 11/13/24 7:57 AM, Juri Lelli wrote: > When root domain non-destructive changes (e.g., only modifying one of > the existing root domains while the rest is not touched) happen we still > need to clear DEADLINE bandwidth accounting so that it's then properly > restore taking into account DEADLINE tasks associated to each cpuset > (associated to each root domain). After the introduction of dl_servers, > we fail to restore such servers contribution after non-destructive > changes (as they are only considered on destructive changes when > runqueues are attached to the new domains). > > Fix this by making sure we iterate over the dl_server attached to > domains that have not been destroyed and add them bandwidth contribution > back correctly. > > Signed-off-by: Juri Lelli > --- > include/linux/sched/deadline.h | 2 +- > kernel/cgroup/cpuset.c | 2 +- > kernel/sched/deadline.c | 18 +++++++++++++----- > kernel/sched/topology.c | 10 ++++++---- > 4 files changed, 21 insertions(+), 11 deletions(-) > > diff --git a/include/linux/sched/deadline.h b/include/linux/sched/deadline.h > index 3a912ab42bb5..82c966a55856 100644 > --- a/include/linux/sched/deadline.h > +++ b/include/linux/sched/deadline.h > @@ -33,7 +33,7 @@ static inline bool dl_time_before(u64 a, u64 b) > > struct root_domain; > extern void dl_add_task_root_domain(struct task_struct *p); > -extern void dl_clear_root_domain(struct root_domain *rd); > +extern void dl_clear_root_domain(struct root_domain *rd, bool restore); > > #endif /* CONFIG_SMP */ > > diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c > index 142303abb055..4d3603a99db3 100644 > --- a/kernel/cgroup/cpuset.c > +++ b/kernel/cgroup/cpuset.c > @@ -954,7 +954,7 @@ static void dl_rebuild_rd_accounting(void) > * Clear default root domain DL accounting, it will be computed again > * if a task belongs to it. > */ > - dl_clear_root_domain(&def_root_domain); > + dl_clear_root_domain(&def_root_domain, false); > > cpuset_for_each_descendant_pre(cs, pos_css, &top_cpuset) { > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > index 9ce93d0bf452..e53208a50279 100644 > --- a/kernel/sched/deadline.c > +++ b/kernel/sched/deadline.c > @@ -2968,13 +2968,21 @@ void dl_add_task_root_domain(struct task_struct *p) > task_rq_unlock(rq, p, &rf); > } > > -void dl_clear_root_domain(struct root_domain *rd) > +void dl_clear_root_domain(struct root_domain *rd, bool restore) > { > - unsigned long flags; > - > - raw_spin_lock_irqsave(&rd->dl_bw.lock, flags); > + guard(raw_spinlock_irqsave)(&rd->dl_bw.lock); > rd->dl_bw.total_bw = 0; > - raw_spin_unlock_irqrestore(&rd->dl_bw.lock, flags); > + > + if (restore) { > + int i; > + > + for_each_cpu(i, rd->span) { > + struct sched_dl_entity *dl_se = &cpu_rq(i)->fair_server; > + > + if (dl_server(dl_se)) > + rd->dl_bw.total_bw += dl_se->dl_bw; > + } > + } > } > > #endif /* CONFIG_SMP */ > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c > index 9748a4c8d668..e9e7a7c43dd6 100644 > --- a/kernel/sched/topology.c > +++ b/kernel/sched/topology.c > @@ -2721,12 +2721,14 @@ void partition_sched_domains_locked(int ndoms_new, cpumask_var_t doms_new[], > > /* > * This domain won't be destroyed and as such > - * its dl_bw->total_bw needs to be cleared. It > - * will be recomputed in function > - * update_tasks_root_domain(). > + * its dl_bw->total_bw needs to be cleared. > + * Tasks contribution will be then recomputed > + * in function dl_update_tasks_root_domain(), > + * dl_servers contribution in function > + * dl_restore_server_root_domain(). > */ > rd = cpu_rq(cpumask_any(doms_cur[i]))->rd; > - dl_clear_root_domain(rd); > + dl_clear_root_domain(rd, true); > goto match1; > } > } With my limited understanding of the deadline code, this change looks reasonable to me. dl_rebuild_rd_accounting() is a part of the cpuset code that is seldom touched. So I don't think this particular hunk will cause any merge conflict. So it can be carried in the tip tree. Acked-by: Waiman Long