From patchwork Wed Nov 30 08:23:02 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tejun Heo X-Patchwork-Id: 13059554 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A0DFDC4321E for ; Wed, 30 Nov 2022 08:26:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235343AbiK3I0m (ORCPT ); Wed, 30 Nov 2022 03:26:42 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56462 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234861AbiK3IZY (ORCPT ); Wed, 30 Nov 2022 03:25:24 -0500 Received: from mail-pg1-x534.google.com (mail-pg1-x534.google.com [IPv6:2607:f8b0:4864:20::534]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0DF4B43AEB; Wed, 30 Nov 2022 00:24:21 -0800 (PST) Received: by mail-pg1-x534.google.com with SMTP id q1so15362119pgl.11; Wed, 30 Nov 2022 00:24:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; 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=3xNLbIsa5gtviYtGbS0XJgTqtP9STFkn3KhLBxJlSY0=; b=EQR4AeKgF7dwfmXpdNFKVBnWmW+pCUqxeTtRwXRJ0+4LEYOg8snYX1U2aIR53pm2GN p8svxnC6OYcJxckHdlLkVzjt69Waao3KPNuqZhTs7FGt7RWAHbaqj+l8TBzeogJNmsn+ mammGiPEkAwPtVELXSq8Rs88LCdIq5gttHc6QbYS6L3s2aPD0yyeiQBECSRRUwJK2wck FZC776aaw2nQbLtwW1uDPTejQ6kUHsXIMgR7dLQ61QjcSCXx7iIcJMts5ncRBeNWsQWJ /XVXd8CgSWlxOTNRiejilc+YTJkzI9qMLGAu8GWNuaeKVrDx02eXKM7SasmXGZASwvKr XdWw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; 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=3xNLbIsa5gtviYtGbS0XJgTqtP9STFkn3KhLBxJlSY0=; b=Thg7bjgkFC7ktYw/33ybMjYoZd4vuAJx6vAGUjJ55DK20WQNG5hRMqGrNN9Lx8VpNR LQo2emkbmuL1MFpqHXi1Du0UGlmZ80k+wti1uLk8sh01soF6Mnsrhs2rbU1C3j4VWXtI 8UuKxPm6f0TwUlLokW1QGlOj74PAFC7TIIOajSM+FKagNX3G3y2k67SSAcr4ceS2BE8y I+BMA5wQk/IPem5xNTM6A3rSiueqoTYpFSW/KTxGBJMOqvIxUOH+x15nDo0uU/uJOJk4 HxfT4HQOVtLWyivIZz/vH5YFodIHjUJ72sTnl30K2xuf0ITkn8HfL8o9ca+kB0wNdcqg 5adw== X-Gm-Message-State: ANoB5pnsP4sV3b07xPlsCA62CR8zp7XfDdsFO78FtIjuffFUgSSrLtVc /jPb2g46qxfT9pA3KtfhL/Y= X-Google-Smtp-Source: AA0mqf52p+ZRo0BmR4ZL/XEv1sKhOHpYfvNqaOh/EtAiX1D/HZyRqbODM6vn6qrOJxKDoS/21Ztu/A== X-Received: by 2002:a63:114b:0:b0:46a:e00b:ada0 with SMTP id 11-20020a63114b000000b0046ae00bada0mr38704577pgr.409.1669796660212; Wed, 30 Nov 2022 00:24:20 -0800 (PST) Received: from localhost ([2600:380:4a00:1415:d028:b547:7d35:7b0b]) by smtp.gmail.com with ESMTPSA id s3-20020a625e03000000b0056bf29c9ba3sm820774pfb.146.2022.11.30.00.24.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Nov 2022 00:24:19 -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 Cc: linux-kernel@vger.kernel.org, bpf@vger.kernel.org, kernel-team@meta.com, Tejun Heo Subject: [PATCH 20/31] sched_ext: Allow BPF schedulers to switch all eligible tasks into sched_ext Date: Tue, 29 Nov 2022 22:23:02 -1000 Message-Id: <20221130082313.3241517-21-tj@kernel.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221130082313.3241517-1-tj@kernel.org> References: <20221130082313.3241517-1-tj@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org 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 dummy and qmap example schedulers are updated with the '-a' option which enables the switch_all behavior. 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 | 42 +++++++++++++++++++++++++ kernel/sched/ext.h | 5 +++ tools/sched_ext/scx_common.bpf.h | 1 + tools/sched_ext/scx_example_dummy.bpf.c | 11 +++++++ tools/sched_ext/scx_example_dummy.c | 8 +++-- tools/sched_ext/scx_example_qmap.bpf.c | 9 ++++++ tools/sched_ext/scx_example_qmap.c | 7 +++-- 8 files changed, 84 insertions(+), 7 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 3404277fed30..20536957840d 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1204,7 +1204,7 @@ 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; return true; @@ -5520,8 +5520,10 @@ void scheduler_tick(void) perf_event_task_tick(); #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 ddd5aa4a8bca..ba0a7a9ea5f2 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -73,6 +73,10 @@ 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 warned_zero_slice; @@ -1844,6 +1848,8 @@ bool task_on_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; } @@ -1982,6 +1988,9 @@ 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); @@ -2159,6 +2168,7 @@ static int scx_ops_enable(struct sched_ext_ops *ops) */ cpus_read_lock(); + scx_switch_all_req = false; if (scx_ops.init) { ret = scx_ops.init(); @@ -2281,6 +2291,8 @@ 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) { @@ -2312,6 +2324,9 @@ static int scx_ops_enable(struct sched_ext_ops *ops) goto err_disable_unlock; } + if (scx_switch_all_req) + static_branch_enable_cpuslocked(&__scx_switched_all); + cpus_read_unlock(); mutex_unlock(&scx_ops_enable_mutex); @@ -2346,6 +2361,9 @@ 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: %llu\n", "nr_rejected", @@ -2586,6 +2604,28 @@ __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 + * @into_scx: switch direction + * + * If @into_scx is %true, all existing and future non-dl/rt tasks are switched + * to SCX. If %false, only tasks which have %SCHED_EXT explicitly set are put on + * SCX. The actual switching is asynchronous. Can be called from ops.init(). + */ +void scx_bpf_switch_all(void) +{ + 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 dsq * @dsq_id: dsq to attach @@ -3015,6 +3055,8 @@ static int __init register_ext_kfuncs(void) * allow all kfuncs for everybody. */ 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_dispatch)) || diff --git a/kernel/sched/ext.h b/kernel/sched/ext.h index 0743a0536560..142dce30764d 100644 --- a/kernel/sched/ext.h +++ b/kernel/sched/ext.h @@ -71,7 +71,9 @@ extern unsigned long task_runnable_timeout_ms; extern unsigned long last_timeout_check; 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) bool task_on_scx(struct task_struct *p); void scx_pre_fork(struct task_struct *p); @@ -108,6 +110,8 @@ 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; @@ -130,6 +134,7 @@ 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 void scx_pre_fork(struct task_struct *p) {} static inline int scx_fork(struct task_struct *p) { return 0; } diff --git a/tools/sched_ext/scx_common.bpf.h b/tools/sched_ext/scx_common.bpf.h index 4cfbbee38d9a..212cb934db2d 100644 --- a/tools/sched_ext/scx_common.bpf.h +++ b/tools/sched_ext/scx_common.bpf.h @@ -48,6 +48,7 @@ void ___scx_bpf_error_format_checker(const char *fmt, ...) {} ___scx_bpf_error_format_checker(fmt, ##args); \ }) +extern void scx_bpf_switch_all(void) __ksym; extern s32 scx_bpf_create_dsq(u64 dsq_id, s32 node) __ksym; extern bool scx_bpf_consume(u64 dsq_id) __ksym; extern u32 scx_bpf_dispatch_nr_slots(void) __ksym; diff --git a/tools/sched_ext/scx_example_dummy.bpf.c b/tools/sched_ext/scx_example_dummy.bpf.c index ac7b490b5a39..28251373d1c3 100644 --- a/tools/sched_ext/scx_example_dummy.bpf.c +++ b/tools/sched_ext/scx_example_dummy.bpf.c @@ -7,6 +7,7 @@ * * - Statistics tracking how many are queued to local and global dsq's. * - Termination notification for userspace. + * - Support for switch_all. * * Copyright (c) 2022 Meta Platforms, Inc. and affiliates. * Copyright (c) 2022 Tejun Heo @@ -16,6 +17,8 @@ char _license[] SEC("license") = "GPL"; +const volatile bool switch_all; + struct user_exit_info uei; struct { @@ -32,6 +35,13 @@ static void stat_inc(u32 idx) (*cnt_p)++; } +s32 BPF_STRUCT_OPS(dummy_init) +{ + if (switch_all) + scx_bpf_switch_all(); + return 0; +} + void BPF_STRUCT_OPS(dummy_enqueue, struct task_struct *p, u64 enq_flags) { if (enq_flags & SCX_ENQ_LOCAL) { @@ -51,6 +61,7 @@ void BPF_STRUCT_OPS(dummy_exit, struct scx_exit_info *ei) SEC(".struct_ops") struct sched_ext_ops dummy_ops = { .enqueue = (void *)dummy_enqueue, + .init = (void *)dummy_init, .exit = (void *)dummy_exit, .name = "dummy", }; diff --git a/tools/sched_ext/scx_example_dummy.c b/tools/sched_ext/scx_example_dummy.c index 72881c881830..9229973e8698 100644 --- a/tools/sched_ext/scx_example_dummy.c +++ b/tools/sched_ext/scx_example_dummy.c @@ -19,8 +19,9 @@ const char help_fmt[] = "\n" "See the top-level comment in .bpf.c for more details.\n" "\n" -"Usage: %s\n" +"Usage: %s [-a]\n" "\n" +" -a Switch all tasks\n" " -h Display this help and exit\n"; static volatile int exit_req; @@ -64,8 +65,11 @@ int main(int argc, char **argv) skel = scx_example_dummy__open(); assert(skel); - while ((opt = getopt(argc, argv, "h")) != -1) { + while ((opt = getopt(argc, argv, "ah")) != -1) { switch (opt) { + case 'a': + skel->rodata->switch_all = true; + break; default: fprintf(stderr, help_fmt, basename(argv[0])); return opt != 'h'; diff --git a/tools/sched_ext/scx_example_qmap.bpf.c b/tools/sched_ext/scx_example_qmap.bpf.c index b6febc5dadbf..bde8cd339935 100644 --- a/tools/sched_ext/scx_example_qmap.bpf.c +++ b/tools/sched_ext/scx_example_qmap.bpf.c @@ -22,6 +22,7 @@ char _license[] SEC("license") = "GPL"; const volatile u64 slice_ns = SCX_SLICE_DFL; +const volatile bool switch_all; const volatile u32 stall_user_nth; const volatile u32 stall_kernel_nth; const volatile s32 disallow_tgid; @@ -223,6 +224,13 @@ s32 BPF_STRUCT_OPS(qmap_prep_enable, struct task_struct *p, return -ENOMEM; } +s32 BPF_STRUCT_OPS(qmap_init) +{ + if (switch_all) + scx_bpf_switch_all(); + return 0; +} + void BPF_STRUCT_OPS(qmap_exit, struct scx_exit_info *ei) { uei_record(&uei, ei); @@ -238,6 +246,7 @@ struct sched_ext_ops qmap_ops = { */ .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_example_qmap.c b/tools/sched_ext/scx_example_qmap.c index 99cc7169bd90..52a44269508b 100644 --- a/tools/sched_ext/scx_example_qmap.c +++ b/tools/sched_ext/scx_example_qmap.c @@ -20,7 +20,7 @@ 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 [-a] [-s SLICE_US] [-e COUNT] [-t COUNT] [-T COUNT] [-d PID]\n" "\n" " -s SLICE_US Override slice duration\n" " -e COUNT Trigger scx_bpf_error() after COUNT enqueues\n" @@ -50,8 +50,11 @@ int main(int argc, char **argv) skel = scx_example_qmap__open(); assert(skel); - while ((opt = getopt(argc, argv, "hs:e:t:T:d:")) != -1) { + while ((opt = getopt(argc, argv, "ahs:e:t:T:d:")) != -1) { switch (opt) { + case 'a': + skel->rodata->switch_all = true; + break; case 's': skel->rodata->slice_ns = strtoull(optarg, NULL, 0) * 1000; break;