From patchwork Tue Jul 11 01:13:45 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tejun Heo X-Patchwork-Id: 13307928 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 844EC3FFA for ; Tue, 11 Jul 2023 01:16:07 +0000 (UTC) Received: from mail-pf1-x434.google.com (mail-pf1-x434.google.com [IPv6:2607:f8b0:4864:20::434]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0B4CF1735; Mon, 10 Jul 2023 18:15:40 -0700 (PDT) Received: by mail-pf1-x434.google.com with SMTP id d2e1a72fcca58-66c729f5618so4463851b3a.1; Mon, 10 Jul 2023 18:15:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1689038111; x=1691630111; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:sender:from:to:cc:subject:date :message-id:reply-to; bh=JVjeLtARNad5J1bPKF5HrYQ+HanLkv7ypO13jcRCNto=; b=sd/f0T/u5gGvdxpjlrjmKTdL+BF/vlQLOHWIqx2p3sV9GH1MgDhLColFgj2iNQh3Vw uc+YpnSGW1OmX+4t8DCKDt7vrx9duDAp4lOIuPpB/M1wnazX9LzyI/MzHluxDs6oSW/t XMb5dA/beaLmvXmoImdisiS/OAoM/Z2v2zktJfTU160P+HNOh91voqEMUwiHt7hhWmGp W7wgVq32+E24/0GaiAFJwO9eZ85R+8e9SRWejM3G37MZfvtBmhShtTdHmxEsj+gPr/xx ApGCfx79jYFYFbqobZLwIqfB4TS+1w+qJB/UHcvCGa3MbwPmgYYt20k/R0h1IhOTdlS8 /zjA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1689038111; x=1691630111; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:sender:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=JVjeLtARNad5J1bPKF5HrYQ+HanLkv7ypO13jcRCNto=; b=OC3jKvTwHADEYrgCRjUkIxM85PhCA1/YThzNrnh7UQWg+7k56QD31IJm4C+sl7lFrO afczcFZuZjvF4V1KaCcTtiTrVDKVcuQrwnCxFf1lo9936M7GQ68WGhQkscN1M8RvV20n lTBuJ0bspkvrd/PAN0MDu0sCWfqRmQ9fBUbgv2VW3fEPp5vGhaTf599b/jbQdvWXTTtS XD79B6sfj2a9feK8W1ioM/tNEnBTEfV2LgQ6Kb5afz4+/OgMoXiCul9tcjn0OgN2/QLT 6Khl1ave2R0ovMXM31frYmvXMNsPMRXKXJNZJS1jHH51+ciS7CKxQ6KYW8uzAnr5bUI5 tcww== X-Gm-Message-State: ABy/qLbDCUl72kkN/dy6gvIiXZIRDxA41md1PjvFoQHpxRsb5MRNZD1U vUlWb/qzEuGy6utF9HKX0M4= X-Google-Smtp-Source: APBJJlGiFEmiQuQeCKe9IV0v6c4BU11DgMJXxpek8dIyDdzpMnRMyh1cgLwtBsdoDfDbkutnL+WgwA== X-Received: by 2002:a05:6a20:104f:b0:12e:c481:7072 with SMTP id gt15-20020a056a20104f00b0012ec4817072mr13936148pzc.37.1689038110551; Mon, 10 Jul 2023 18:15:10 -0700 (PDT) Received: from localhost ([2620:10d:c090:400::5:e2fe]) by smtp.gmail.com with ESMTPSA id j13-20020a62b60d000000b0064928cb5f03sm405656pff.69.2023.07.10.18.15.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 Jul 2023 18:15:10 -0700 (PDT) Sender: Tejun Heo From: Tejun Heo To: torvalds@linux-foundation.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@kernel.org, joshdon@google.com, brho@google.com, pjt@google.com, derkling@google.com, haoluo@google.com, dvernet@meta.com, dschatzberg@meta.com, dskarlat@cs.cmu.edu, riel@surriel.com Cc: linux-kernel@vger.kernel.org, bpf@vger.kernel.org, kernel-team@meta.com, Tejun Heo Subject: [PATCH 27/34] sched_ext: Implement SCX_KICK_WAIT Date: Mon, 10 Jul 2023 15:13:45 -1000 Message-ID: <20230711011412.100319-28-tj@kernel.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230711011412.100319-1-tj@kernel.org> References: <20230711011412.100319-1-tj@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Spam-Status: No, score=-1.5 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_EF,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_BLOCKED,SPF_HELO_NONE, SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net From: David Vernet If set when calling scx_bpf_kick_cpu(), the invoking CPU will busy wait for the kicked cpu to enter the scheduler. This will be used to improve the exclusion guarantees in scx_pair. Signed-off-by: David Vernet Reviewed-by: Tejun Heo Signed-off-by: Tejun Heo Acked-by: Josh Don Acked-by: Hao Luo Acked-by: Barret Rhoden --- kernel/sched/core.c | 4 +++- kernel/sched/ext.c | 33 ++++++++++++++++++++++++++++++++- kernel/sched/ext.h | 20 ++++++++++++++++++++ kernel/sched/sched.h | 2 ++ 4 files changed, 57 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 77eb4ee4f759..878e84694a6e 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6052,8 +6052,10 @@ __pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) for_each_active_class(class) { p = class->pick_next_task(rq); - if (p) + if (p) { + scx_notify_pick_next_task(rq, p, class); return p; + } } BUG(); /* The idle class should always have a runnable task. */ diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index 5862e8290207..48a8881ff01f 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -125,6 +125,9 @@ static struct { #endif /* CONFIG_SMP */ +/* for %SCX_KICK_WAIT */ +static u64 __percpu *scx_kick_cpus_pnt_seqs; + /* * Direct dispatch marker. * @@ -3269,6 +3272,7 @@ static const struct sysrq_key_op sysrq_sched_ext_reset_op = { static void kick_cpus_irq_workfn(struct irq_work *irq_work) { struct rq *this_rq = this_rq(); + u64 *pseqs = this_cpu_ptr(scx_kick_cpus_pnt_seqs); int this_cpu = cpu_of(this_rq); int cpu; @@ -3282,14 +3286,32 @@ static void kick_cpus_irq_workfn(struct irq_work *irq_work) if (cpumask_test_cpu(cpu, this_rq->scx.cpus_to_preempt) && rq->curr->sched_class == &ext_sched_class) rq->curr->scx.slice = 0; + pseqs[cpu] = rq->scx.pnt_seq; resched_curr(rq); + } else { + cpumask_clear_cpu(cpu, this_rq->scx.cpus_to_wait); } raw_spin_rq_unlock_irqrestore(rq, flags); } + for_each_cpu_andnot(cpu, this_rq->scx.cpus_to_wait, + cpumask_of(this_cpu)) { + /* + * Pairs with smp_store_release() issued by this CPU in + * scx_notify_pick_next_task() on the resched path. + * + * We busy-wait here to guarantee that no other task can be + * scheduled on our core before the target CPU has entered the + * resched path. + */ + while (smp_load_acquire(&cpu_rq(cpu)->scx.pnt_seq) == pseqs[cpu]) + cpu_relax(); + } + cpumask_clear(this_rq->scx.cpus_to_kick); cpumask_clear(this_rq->scx.cpus_to_preempt); + cpumask_clear(this_rq->scx.cpus_to_wait); } void __init init_sched_ext_class(void) @@ -3303,7 +3325,7 @@ void __init init_sched_ext_class(void) * through the generated vmlinux.h. */ WRITE_ONCE(v, SCX_WAKE_EXEC | SCX_ENQ_WAKEUP | SCX_DEQ_SLEEP | - SCX_TG_ONLINE); + SCX_TG_ONLINE | SCX_KICK_PREEMPT); BUG_ON(rhashtable_init(&dsq_hash, &dsq_hash_params)); init_dsq(&scx_dsq_global, SCX_DSQ_GLOBAL); @@ -3311,6 +3333,12 @@ void __init init_sched_ext_class(void) BUG_ON(!alloc_cpumask_var(&idle_masks.cpu, GFP_KERNEL)); BUG_ON(!alloc_cpumask_var(&idle_masks.smt, GFP_KERNEL)); #endif + scx_kick_cpus_pnt_seqs = + __alloc_percpu(sizeof(scx_kick_cpus_pnt_seqs[0]) * + num_possible_cpus(), + __alignof__(scx_kick_cpus_pnt_seqs[0])); + BUG_ON(!scx_kick_cpus_pnt_seqs); + for_each_possible_cpu(cpu) { struct rq *rq = cpu_rq(cpu); @@ -3319,6 +3347,7 @@ void __init init_sched_ext_class(void) BUG_ON(!zalloc_cpumask_var(&rq->scx.cpus_to_kick, GFP_KERNEL)); BUG_ON(!zalloc_cpumask_var(&rq->scx.cpus_to_preempt, GFP_KERNEL)); + BUG_ON(!zalloc_cpumask_var(&rq->scx.cpus_to_wait, GFP_KERNEL)); init_irq_work(&rq->scx.kick_cpus_irq_work, kick_cpus_irq_workfn); } @@ -3585,6 +3614,8 @@ void scx_bpf_kick_cpu(s32 cpu, u64 flags) cpumask_set_cpu(cpu, rq->scx.cpus_to_kick); if (flags & SCX_KICK_PREEMPT) cpumask_set_cpu(cpu, rq->scx.cpus_to_preempt); + if (flags & SCX_KICK_WAIT) + cpumask_set_cpu(cpu, rq->scx.cpus_to_wait); irq_work_queue(&rq->scx.kick_cpus_irq_work); preempt_enable(); diff --git a/kernel/sched/ext.h b/kernel/sched/ext.h index c3404a0a7637..abb283ac3bc7 100644 --- a/kernel/sched/ext.h +++ b/kernel/sched/ext.h @@ -65,6 +65,7 @@ enum scx_pick_idle_cpu_flags { enum scx_kick_flags { SCX_KICK_PREEMPT = 1LLU << 0, /* force scheduling on the CPU */ + SCX_KICK_WAIT = 1LLU << 1, /* wait for the CPU to be rescheduled */ }; enum scx_tg_flags { @@ -115,6 +116,22 @@ __printf(2, 3) void scx_ops_error_type(enum scx_exit_type type, #define scx_ops_error(fmt, args...) \ scx_ops_error_type(SCX_EXIT_ERROR, fmt, ##args) +static inline void scx_notify_pick_next_task(struct rq *rq, + const struct task_struct *p, + const struct sched_class *active) +{ +#ifdef CONFIG_SMP + if (!scx_enabled()) + return; + /* + * Pairs with the smp_load_acquire() issued by a CPU in + * kick_cpus_irq_workfn() who is waiting for this CPU to perform a + * resched. + */ + smp_store_release(&rq->scx.pnt_seq, rq->scx.pnt_seq + 1); +#endif +} + static inline void scx_notify_sched_tick(void) { unsigned long last_check; @@ -170,6 +187,9 @@ static inline int scx_check_setscheduler(struct task_struct *p, int policy) { return 0; } static inline bool scx_can_stop_tick(struct rq *rq) { return true; } static inline void init_sched_ext_class(void) {} +static inline void scx_notify_pick_next_task(struct rq *rq, + const struct task_struct *p, + const struct sched_class *active) {} static inline void scx_notify_sched_tick(void) {} #define for_each_active_class for_each_class diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 00bf33fdbd64..ce6e0a73135b 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -710,6 +710,8 @@ struct scx_rq { u32 flags; cpumask_var_t cpus_to_kick; cpumask_var_t cpus_to_preempt; + cpumask_var_t cpus_to_wait; + u64 pnt_seq; struct irq_work kick_cpus_irq_work; }; #endif /* CONFIG_SCHED_CLASS_EXT */