From nobody Mon Feb 9 17:23:29 2026 Received: from fanzine2.igalia.com (fanzine.igalia.com [178.60.130.6]) (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 E8D3613A3ED for ; Fri, 31 Jan 2025 07:10:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=178.60.130.6 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738307404; cv=none; b=T1tymZThtEbtIL2DvJQIS0x7Aglo23XFJi2nvIgFO5DqGoXWMn9FTjUis2MCkKQvxSEVRUJqOQQuJSjh/IL5wMikAf+pcytAIOkCyZs2Bb//UaKF1bcQ6LwAJadXsy1FjazPvwHbVwg4pE2zwdAyhxtrl5gz+I5UbnyrWBM6w0o= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738307404; c=relaxed/simple; bh=EVM2OyD7ITS8CjCs3HeW0si0C7xpIaQVqCPuwTKw9aE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=M9FWIVf1CvaIy7tT1nMQjwqU9+ZdGUlywib9vb1eeynElscoAHNH0KX91JXf5mdG8oCW+wRsrZRsNjjuWY80SZLMu17Xko0DDDEO2Olc06KqtRvRxGQTjFMJncrqUL9uK7kS6k7BYP9lpdeMT/JrmiJ/BYoT1caaY02LJAS25UA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=igalia.com; spf=pass smtp.mailfrom=igalia.com; dkim=pass (2048-bit key) header.d=igalia.com header.i=@igalia.com header.b=Pa1dEgA8; arc=none smtp.client-ip=178.60.130.6 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=igalia.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=igalia.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=igalia.com header.i=@igalia.com header.b="Pa1dEgA8" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Transfer-Encoding:MIME-Version:References:In-Reply-To: Message-ID:Date:Subject:Cc:To:From:Sender:Reply-To:Content-Type:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=bGbZyxBQi2Nkt3T6KZ5le7N8O0Lnv0KnbNQBek0nrjI=; b=Pa1dEgA8aZuwFenNNcmqidmZFL ngWjhImKhX/rV0+U6jcz0YxWrJJlX10VzfUj9Ee79R6es2vqKS8VbQxf5ZNPYIvjWvstUPwOcZS84 cEIbvmx7TXTuim9vyf4mMF8GuUSMBNMn+HEaaF49Zf2jHDX1EFnhlqwhrSgkZFoNvw0zpey93bVLR vjdefWPbfnfTNs+NzfqGkVk3YNiuRR4/EzresgcNKsZ7NqBYCSELoFRF4W3s+WfeKEDJ8Fz21I5tw aG0bg1vNLTWIEucw6wykMUOh8aM/gkj7U1BQlnW5iuRs8RCOcNvjKwIlFI6eZubWZZf3knSskxNb8 sLfEbh6w==; Received: from [58.29.143.236] (helo=localhost) by fanzine2.igalia.com with utf8esmtpsa (Cipher TLS1.3:ECDHE_SECP256R1__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim) id 1tdl9x-001KYP-Lz; Fri, 31 Jan 2025 08:09:56 +0100 From: Changwoo Min To: tj@kernel.org, void@manifault.com, arighi@nvidia.com Cc: kernel-dev@igalia.com, linux-kernel@vger.kernel.org, Changwoo Min Subject: [PATCH v3 02/11] sched_ext: Add an event, SCX_EV_SELECT_CPU_FALLBACK Date: Fri, 31 Jan 2025 16:09:29 +0900 Message-ID: <20250131070938.95551-3-changwoo@igalia.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250131070938.95551-1-changwoo@igalia.com> References: <20250131070938.95551-1-changwoo@igalia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add a core event, SCX_EV_SELECT_CPU_FALLBACK, which represents how many tim= es ops.select_cpu() returns a CPU that the task can't use. __scx_add_event() is used since the caller holds an rq lock, so the preemption has already been disabled. Signed-off-by: Changwoo Min --- include/linux/sched/ext.h | 1 + kernel/sched/ext.c | 14 ++++++++++++++ 2 files changed, 15 insertions(+) diff --git a/include/linux/sched/ext.h b/include/linux/sched/ext.h index 1d70a9867fb1..f7545430a548 100644 --- a/include/linux/sched/ext.h +++ b/include/linux/sched/ext.h @@ -146,6 +146,7 @@ struct sched_ext_entity { u32 weight; s32 sticky_cpu; s32 holding_cpu; + s32 selected_cpu; u32 kf_mask; /* see scx_kf_mask above */ struct task_struct *kf_tasks[2]; /* see SCX_CALL_OP_TASK() */ atomic_long_t ops_state; diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index 4e28e88e88d4..4d3b32aca48d 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -1444,6 +1444,11 @@ static struct task_struct *scx_task_iter_next_locked= (struct scx_task_iter *iter) * Collection of event counters. Event types are placed in descending orde= r. */ struct scx_event_stats { + /* + * If ops.select_cpu() returns a CPU which can't be used by the task, + * the core scheduler code silently picks a fallback CPU. + */ + u64 SCX_EV_SELECT_CPU_FALLBACK; }; =20 /* @@ -2170,6 +2175,11 @@ static void enqueue_task_scx(struct rq *rq, struct t= ask_struct *p, int enq_flags do_enqueue_task(rq, p, enq_flags, sticky_cpu); out: rq->scx.flags &=3D ~SCX_RQ_IN_WAKEUP; + + if ((enq_flags & SCX_ENQ_CPU_SELECTED) && + (cpu_of(rq) !=3D p->scx.selected_cpu)) { + __scx_add_event(SCX_EV_SELECT_CPU_FALLBACK, 1); + } } =20 static void ops_dequeue(struct task_struct *p, u64 deq_flags) @@ -3240,6 +3250,7 @@ static int select_task_rq_scx(struct task_struct *p, = int prev_cpu, int wake_flag =20 cpu =3D SCX_CALL_OP_TASK_RET(SCX_KF_ENQUEUE | SCX_KF_SELECT_CPU, select_cpu, p, prev_cpu, wake_flags); + p->scx.selected_cpu =3D cpu; *ddsp_taskp =3D NULL; if (ops_cpu_valid(cpu, "from ops.select_cpu()")) return cpu; @@ -3250,6 +3261,7 @@ static int select_task_rq_scx(struct task_struct *p, = int prev_cpu, int wake_flag s32 cpu; =20 cpu =3D scx_select_cpu_dfl(p, prev_cpu, wake_flags, &found); + p->scx.selected_cpu =3D cpu; if (found) { p->scx.slice =3D SCX_SLICE_DFL; p->scx.ddsp_dsq_id =3D SCX_DSQ_LOCAL; @@ -4957,6 +4969,7 @@ static void scx_dump_state(struct scx_exit_info *ei, = size_t dump_len) dump_line(&s, "--------------"); =20 scx_bpf_events(&events, sizeof(events)); + scx_dump_event(s, &events, SCX_EV_SELECT_CPU_FALLBACK); =20 if (seq_buf_has_overflowed(&s) && dump_len >=3D sizeof(trunc_marker)) memcpy(ei->dump + dump_len - sizeof(trunc_marker), @@ -7090,6 +7103,7 @@ __bpf_kfunc void scx_bpf_events(struct scx_event_stat= s *events, memset(&e_sys, 0, sizeof(e_sys)); for_each_possible_cpu(cpu) { e_cpu =3D per_cpu_ptr(&event_stats_cpu, cpu); + scx_agg_event(&e_sys, e_cpu, SCX_EV_SELECT_CPU_FALLBACK); } =20 /* --=20 2.48.1