From patchwork Sat Nov 11 02:47:43 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tejun Heo X-Patchwork-Id: 13452942 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 ACDFC53B5 for ; Sat, 11 Nov 2023 02:51:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="dMAn25/E" Received: from mail-oi1-x230.google.com (mail-oi1-x230.google.com [IPv6:2607:f8b0:4864:20::230]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E56784EC3; Fri, 10 Nov 2023 18:49:28 -0800 (PST) Received: by mail-oi1-x230.google.com with SMTP id 5614622812f47-3b566ee5f1dso1441821b6e.0; Fri, 10 Nov 2023 18:49:28 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1699670968; x=1700275768; darn=vger.kernel.org; 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=cCDpGBaTShbaonGJEwLXrDohmcOtEf6xm+ibDWlEcqg=; b=dMAn25/ErODxdg8H+KlW7dm3xbrLyI/yVih1RwxAStbrUhQj1tk8GCNbSvzw/3hWSZ 226OLqZ/FGFDlMWGNPvJLhhyWgd10b+s3ACf9J39oCmMBfbXzlPw8LaUeFon3AJsWaft FPflM92lUn4s8q+2O8LeMkpxvNri8KqmQ4Ev8mCHr7/1DGeDBfFqjTgrVj8J177Cyf3K YsH8o+nG0ZdmkZA5powmjHbka0ZJPF81OgzzFSycspE3W0+jvxPv0Xn53Vs7SOQJuN8d VEOYYTW07jCCdAEdNi/BJQuBtI79VpVxpF4NmNIPA1KHiaL5dc1e0YWzGvBPci8sH8oz m8kA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1699670968; x=1700275768; 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=cCDpGBaTShbaonGJEwLXrDohmcOtEf6xm+ibDWlEcqg=; b=FagklpE7UWFz2T/6RxbkpU9n0c/Fk2YLFkYLBrLhPXm4MC7WfKRNKGJUFPthQA0cjj V/2df11htXMsLYJWe8ywvgh0mj4nqU4G/+mv0jYTsLxtzOHQX0N/bDvGGq7WBQHu39Dv AA2kalU7bNR+17PNa64lripHCJHc5xA8hn2/4GHrEXBzVc+7JIE1ZJB5YwP76JWR6Z7u D0IWXwJKPNv7ZyFn1sBe2dBwvPt+lbU6KyXqz4ymROt8nPm79TL/ZtBHkl6q/9YV34HD GUT8ekQFhTBnXAGG/Z7TR59tI/zknDgw4OWSAJLNs61cj+ROGP3RvjDiefG4cNmkKDDJ DTuw== X-Gm-Message-State: AOJu0YxECiEMU34SohePA8c2Uxysogk7G8ZrZBWtTtocUZuyJVwihS4i iw/t4cD4w3LpRv7tEuIrUKM= X-Google-Smtp-Source: AGHT+IHoHobf+lpvQG/wBuXZRSpnU/WQ48NOwBPiPujSI6PcZmXqlKo9xxH4ZLEQcwgnmZX7V9CMeA== X-Received: by 2002:aca:1909:0:b0:3af:b6d3:cda0 with SMTP id l9-20020aca1909000000b003afb6d3cda0mr1199936oii.40.1699670967980; Fri, 10 Nov 2023 18:49:27 -0800 (PST) Received: from localhost ([2620:10d:c090:400::4:7384]) by smtp.gmail.com with ESMTPSA id v8-20020aa78088000000b006c31c239345sm405260pff.177.2023.11.10.18.49.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 10 Nov 2023 18:49:27 -0800 (PST) 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, changwoo@igalia.com, himadrics@inria.fr, memxor@gmail.com Cc: linux-kernel@vger.kernel.org, bpf@vger.kernel.org, kernel-team@meta.com, Tejun Heo Subject: [PATCH 17/36] sched_ext: Allow BPF schedulers to switch all eligible tasks into sched_ext Date: Fri, 10 Nov 2023 16:47:43 -1000 Message-ID: <20231111024835.2164816-18-tj@kernel.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231111024835.2164816-1-tj@kernel.org> References: <20231111024835.2164816-1-tj@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Currently, to use sched_ext, each task has to be put into sched_ext using sched_setscheduler(2). However, some BPF schedulers and use cases might prefer to service all eligible tasks. This patch adds a new kfunc helper, scx_bpf_switch_all(), that BPF schedulers can call from ops.init() to switch all SCHED_NORMAL, SCHED_BATCH and SCHED_IDLE tasks into sched_ext. This has the benefit that the scheduler swaps are transparent to the users and applications. As we know that CFS is not being used when scx_bpf_switch_all() is used, we can also disable hot path entry points with static_branches. Both the simple and qmap example schedulers are updated to switch all tasks by default to ease testing. '-p' option is added which enables the original behavior of switching only tasks which are explicitly on SCHED_EXT. v2: In the example schedulers, switch all tasks by default. Signed-off-by: Tejun Heo Suggested-by: Barret Rhoden Reviewed-by: David Vernet Acked-by: Josh Don Acked-by: Hao Luo Acked-by: Barret Rhoden --- kernel/sched/core.c | 8 +++--- kernel/sched/ext.c | 43 ++++++++++++++++++++++++++++++++ kernel/sched/ext.h | 5 ++++ tools/sched_ext/scx_common.bpf.h | 1 + tools/sched_ext/scx_qmap.bpf.c | 9 +++++++ tools/sched_ext/scx_qmap.c | 8 ++++-- tools/sched_ext/scx_simple.bpf.c | 10 ++++++++ tools/sched_ext/scx_simple.c | 8 ++++-- 8 files changed, 85 insertions(+), 7 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 6b8883fedf33..1906f8397c28 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1236,7 +1236,7 @@ bool sched_can_stop_tick(struct rq *rq) * if there's more than one we need the tick for involuntary * preemption. */ - if (rq->nr_running > 1) + if (!scx_switched_all() && rq->nr_running > 1) return false; /* @@ -5723,8 +5723,10 @@ void scheduler_tick(void) wq_worker_tick(curr); #ifdef CONFIG_SMP - rq->idle_balance = idle_cpu(cpu); - trigger_load_balance(rq); + if (!scx_switched_all()) { + rq->idle_balance = idle_cpu(cpu); + trigger_load_balance(rq); + } #endif } diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index 025b6103b87d..4e2aa9f308fb 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -80,6 +80,10 @@ static DEFINE_MUTEX(scx_ops_enable_mutex); DEFINE_STATIC_KEY_FALSE(__scx_ops_enabled); DEFINE_STATIC_PERCPU_RWSEM(scx_fork_rwsem); static atomic_t scx_ops_enable_state_var = ATOMIC_INIT(SCX_OPS_DISABLED); +static bool scx_switch_all_req; +static bool scx_switching_all; +DEFINE_STATIC_KEY_FALSE(__scx_switched_all); + static struct sched_ext_ops scx_ops; static bool scx_warned_zero_slice; @@ -2068,6 +2072,8 @@ bool task_should_scx(struct task_struct *p) { if (!scx_enabled() || scx_ops_disabling()) return false; + if (READ_ONCE(scx_switching_all)) + return true; return p->policy == SCHED_EXT; } @@ -2195,6 +2201,9 @@ static void scx_ops_disable_workfn(struct kthread_work *work) */ mutex_lock(&scx_ops_enable_mutex); + static_branch_disable(&__scx_switched_all); + WRITE_ONCE(scx_switching_all, false); + /* avoid racing against fork */ cpus_read_lock(); percpu_down_write(&scx_fork_rwsem); @@ -2378,6 +2387,7 @@ static int scx_ops_enable(struct sched_ext_ops *ops) */ cpus_read_lock(); + scx_switch_all_req = false; if (scx_ops.init) { ret = SCX_CALL_OP_RET(SCX_KF_INIT, init); if (ret) { @@ -2493,6 +2503,8 @@ static int scx_ops_enable(struct sched_ext_ops *ops) * transitions here are synchronized against sched_ext_free() through * scx_tasks_lock. */ + WRITE_ONCE(scx_switching_all, scx_switch_all_req); + scx_task_iter_init(&sti); while ((p = scx_task_iter_next_filtered_locked(&sti))) { if (READ_ONCE(p->__state) != TASK_DEAD) { @@ -2524,6 +2536,9 @@ static int scx_ops_enable(struct sched_ext_ops *ops) goto err_disable; } + if (scx_switch_all_req) + static_branch_enable_cpuslocked(&__scx_switched_all); + cpus_read_unlock(); mutex_unlock(&scx_ops_enable_mutex); @@ -2558,6 +2573,9 @@ static int scx_debug_show(struct seq_file *m, void *v) mutex_lock(&scx_ops_enable_mutex); seq_printf(m, "%-30s: %s\n", "ops", scx_ops.name); seq_printf(m, "%-30s: %ld\n", "enabled", scx_enabled()); + seq_printf(m, "%-30s: %d\n", "switching_all", + READ_ONCE(scx_switching_all)); + seq_printf(m, "%-30s: %ld\n", "switched_all", scx_switched_all()); seq_printf(m, "%-30s: %s\n", "enable_state", scx_ops_enable_state_str[scx_ops_enable_state()]); seq_printf(m, "%-30s: %lu\n", "nr_rejected", @@ -2809,6 +2827,29 @@ __diag_push(); __diag_ignore_all("-Wmissing-prototypes", "Global functions as their definitions will be in vmlinux BTF"); +/** + * scx_bpf_switch_all - Switch all tasks into SCX + * + * Switch all existing and future non-dl/rt tasks to SCX. This can only be + * called from ops.init(), and actual switching is performed asynchronously. + */ +void scx_bpf_switch_all(void) +{ + if (!scx_kf_allowed(SCX_KF_INIT)) + return; + + scx_switch_all_req = true; +} + +BTF_SET8_START(scx_kfunc_ids_init) +BTF_ID_FLAGS(func, scx_bpf_switch_all) +BTF_SET8_END(scx_kfunc_ids_init) + +static const struct btf_kfunc_id_set scx_kfunc_set_init = { + .owner = THIS_MODULE, + .set = &scx_kfunc_ids_init, +}; + /** * scx_bpf_create_dsq - Create a custom DSQ * @dsq_id: DSQ to create @@ -3312,6 +3353,8 @@ static int __init register_ext_kfuncs(void) * check using scx_kf_allowed(). */ if ((ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, + &scx_kfunc_set_init)) || + (ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, &scx_kfunc_set_sleepable)) || (ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, &scx_kfunc_set_enqueue_dispatch)) || diff --git a/kernel/sched/ext.h b/kernel/sched/ext.h index bd283ee54da7..1cdef69a6855 100644 --- a/kernel/sched/ext.h +++ b/kernel/sched/ext.h @@ -75,7 +75,9 @@ extern unsigned long scx_watchdog_timeout; extern unsigned long scx_watchdog_timestamp; DECLARE_STATIC_KEY_FALSE(__scx_ops_enabled); +DECLARE_STATIC_KEY_FALSE(__scx_switched_all); #define scx_enabled() static_branch_unlikely(&__scx_ops_enabled) +#define scx_switched_all() static_branch_unlikely(&__scx_switched_all) static inline bool task_on_scx(const struct task_struct *p) { @@ -115,6 +117,8 @@ static inline void scx_notify_sched_tick(void) static inline const struct sched_class *next_active_class(const struct sched_class *class) { class++; + if (scx_switched_all() && class == &fair_sched_class) + class++; if (!scx_enabled() && class == &ext_sched_class) class++; return class; @@ -137,6 +141,7 @@ static inline const struct sched_class *next_active_class(const struct sched_cla #else /* CONFIG_SCHED_CLASS_EXT */ #define scx_enabled() false +#define scx_switched_all() false static inline bool task_on_scx(const struct task_struct *p) { return false; } static inline void scx_pre_fork(struct task_struct *p) {} diff --git a/tools/sched_ext/scx_common.bpf.h b/tools/sched_ext/scx_common.bpf.h index cfd3122244eb..81e484defd9b 100644 --- a/tools/sched_ext/scx_common.bpf.h +++ b/tools/sched_ext/scx_common.bpf.h @@ -53,6 +53,7 @@ void ___scx_bpf_error_format_checker(const char *fmt, ...) {} ___scx_bpf_error_format_checker(fmt, ##args); \ }) +void scx_bpf_switch_all(void) __ksym; s32 scx_bpf_create_dsq(u64 dsq_id, s32 node) __ksym; bool scx_bpf_consume(u64 dsq_id) __ksym; u32 scx_bpf_dispatch_nr_slots(void) __ksym; diff --git a/tools/sched_ext/scx_qmap.bpf.c b/tools/sched_ext/scx_qmap.bpf.c index d0bc67095062..da43f962ab4e 100644 --- a/tools/sched_ext/scx_qmap.bpf.c +++ b/tools/sched_ext/scx_qmap.bpf.c @@ -25,6 +25,7 @@ char _license[] SEC("license") = "GPL"; const volatile u64 slice_ns = SCX_SLICE_DFL; +const volatile bool switch_partial; const volatile u32 stall_user_nth; const volatile u32 stall_kernel_nth; const volatile s32 disallow_tgid; @@ -239,6 +240,13 @@ s32 BPF_STRUCT_OPS(qmap_prep_enable, struct task_struct *p, return -ENOMEM; } +s32 BPF_STRUCT_OPS(qmap_init) +{ + if (!switch_partial) + scx_bpf_switch_all(); + return 0; +} + void BPF_STRUCT_OPS(qmap_exit, struct scx_exit_info *ei) { uei_record(&uei, ei); @@ -251,6 +259,7 @@ struct sched_ext_ops qmap_ops = { .dequeue = (void *)qmap_dequeue, .dispatch = (void *)qmap_dispatch, .prep_enable = (void *)qmap_prep_enable, + .init = (void *)qmap_init, .exit = (void *)qmap_exit, .timeout_ms = 5000U, .name = "qmap", diff --git a/tools/sched_ext/scx_qmap.c b/tools/sched_ext/scx_qmap.c index 6002cef833ab..cac9f0780ce9 100644 --- a/tools/sched_ext/scx_qmap.c +++ b/tools/sched_ext/scx_qmap.c @@ -18,13 +18,14 @@ const char help_fmt[] = "\n" "See the top-level comment in .bpf.c for more details.\n" "\n" -"Usage: %s [-s SLICE_US] [-e COUNT] [-t COUNT] [-T COUNT] [-d PID]\n" +"Usage: %s [-s SLICE_US] [-e COUNT] [-t COUNT] [-T COUNT] [-d PID] [-p]\n" "\n" " -s SLICE_US Override slice duration\n" " -e COUNT Trigger scx_bpf_error() after COUNT enqueues\n" " -t COUNT Stall every COUNT'th user thread\n" " -T COUNT Stall every COUNT'th kernel thread\n" " -d PID Disallow a process from switching into SCHED_EXT (-1 for self)\n" +" -p Switch only tasks on SCHED_EXT policy intead of all\n" " -h Display this help and exit\n"; static volatile int exit_req; @@ -48,7 +49,7 @@ int main(int argc, char **argv) skel = scx_qmap__open(); SCX_BUG_ON(!skel, "Failed to open skel"); - while ((opt = getopt(argc, argv, "s:e:t:T:d:h")) != -1) { + while ((opt = getopt(argc, argv, "s:e:t:T:d:ph")) != -1) { switch (opt) { case 's': skel->rodata->slice_ns = strtoull(optarg, NULL, 0) * 1000; @@ -67,6 +68,9 @@ int main(int argc, char **argv) if (skel->rodata->disallow_tgid < 0) skel->rodata->disallow_tgid = getpid(); break; + case 'p': + skel->rodata->switch_partial = true; + break; default: fprintf(stderr, help_fmt, basename(argv[0])); return opt != 'h'; diff --git a/tools/sched_ext/scx_simple.bpf.c b/tools/sched_ext/scx_simple.bpf.c index 9326124a32fa..6302a4ea9ea5 100644 --- a/tools/sched_ext/scx_simple.bpf.c +++ b/tools/sched_ext/scx_simple.bpf.c @@ -15,6 +15,8 @@ char _license[] SEC("license") = "GPL"; +const volatile bool switch_partial; + struct user_exit_info uei; struct { @@ -43,6 +45,13 @@ void BPF_STRUCT_OPS(simple_enqueue, struct task_struct *p, u64 enq_flags) scx_bpf_dispatch(p, SCX_DSQ_GLOBAL, SCX_SLICE_DFL, enq_flags); } +s32 BPF_STRUCT_OPS(simple_init) +{ + if (!switch_partial) + scx_bpf_switch_all(); + return 0; +} + void BPF_STRUCT_OPS(simple_exit, struct scx_exit_info *ei) { uei_record(&uei, ei); @@ -51,6 +60,7 @@ void BPF_STRUCT_OPS(simple_exit, struct scx_exit_info *ei) SEC(".struct_ops.link") struct sched_ext_ops simple_ops = { .enqueue = (void *)simple_enqueue, + .init = (void *)simple_init, .exit = (void *)simple_exit, .name = "simple", }; diff --git a/tools/sched_ext/scx_simple.c b/tools/sched_ext/scx_simple.c index c282674af8c3..6116b13d8cff 100644 --- a/tools/sched_ext/scx_simple.c +++ b/tools/sched_ext/scx_simple.c @@ -17,8 +17,9 @@ const char help_fmt[] = "\n" "See the top-level comment in .bpf.c for more details.\n" "\n" -"Usage: %s\n" +"Usage: %s [-p]\n" "\n" +" -p Switch only tasks on SCHED_EXT policy intead of all\n" " -h Display this help and exit\n"; static volatile int exit_req; @@ -62,8 +63,11 @@ int main(int argc, char **argv) skel = scx_simple__open(); SCX_BUG_ON(!skel, "Failed to open skel"); - while ((opt = getopt(argc, argv, "h")) != -1) { + while ((opt = getopt(argc, argv, "ph")) != -1) { switch (opt) { + case 'p': + skel->rodata->switch_partial = true; + break; default: fprintf(stderr, help_fmt, basename(argv[0])); return opt != 'h';