From nobody Sun Oct 5 20:15:19 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 948E6296148 for ; Wed, 30 Jul 2025 13:12:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753881138; cv=none; b=oIb2Ag/2aBesGvvWKdEPNjNRncPRhujawhfXgXMcH5RR9IVqvMXVjEXHVMCYVDwuFuXb5Z0l5zJ29WTYHnGrHbzFPKeSwWQtaVzkZw99PQ76R0AhWU8mEMtASgLP8G145ZKIVdPH5RQrmHjxGFLYz4nxIH0zJXQlknubOBMk/WE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753881138; c=relaxed/simple; bh=PAuC7WsD1zBs+mST80zzb6TiYFjZslit6K2f3rxKY44=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Z90BwJrPrX7U1n7+v+v18Y8w2MeUQS6vjjAUnm5wmzV1TTUkJsw7BJVVIb55+mZFJiRhKmVCJTkFePWNe9n4rxYyQWW26ZlMPRYfgjryfWbhQXbOW6T3WiI1Ywxpj3NPH75bh96gh8EUqMqh0c852/xRLLdQAQhjo0bKEU0Zr5s= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=F5nLKzVX; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="F5nLKzVX" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1753881135; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=tdFBLnsCWpckgB9HbqcHHM/hdZ93c/I5FsM9wN8QhNI=; b=F5nLKzVX6JSu9zkzpxLFhs83mIXLCe5ERbcbauoyw2nVuyHKqCV64swhZksvAXIWu1QMUW QHil7Z5I4Z3SsAAUpC0HvNgJrKuwqq4P4u/3BQoV4VLdRyC2gBAc0TgPdTg1JanG+umSwC 7CvJGTmuycwNfVyhkY8Dpzv/DNnsJck= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-128-lDsU7437M0uA6WZMlWc3UQ-1; Wed, 30 Jul 2025 09:12:11 -0400 X-MC-Unique: lDsU7437M0uA6WZMlWc3UQ-1 X-Mimecast-MFC-AGG-ID: lDsU7437M0uA6WZMlWc3UQ_1753881130 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 93ED91956096; Wed, 30 Jul 2025 13:12:10 +0000 (UTC) Received: from gmonaco-thinkpadt14gen3.rmtit.com (unknown [10.44.33.26]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 52CBA19560A2; Wed, 30 Jul 2025 13:12:07 +0000 (UTC) From: Gabriele Monaco To: linux-kernel@vger.kernel.org, Anna-Maria Behnsen , Frederic Weisbecker , Thomas Gleixner , Waiman Long Cc: Gabriele Monaco Subject: [PATCH v9 1/8] timers/migration: Postpone online/offline callbacks registration to late initcall Date: Wed, 30 Jul 2025 15:11:51 +0200 Message-ID: <20250730131158.101668-2-gmonaco@redhat.com> In-Reply-To: <20250730131158.101668-1-gmonaco@redhat.com> References: <20250730131158.101668-1-gmonaco@redhat.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 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Content-Type: text/plain; charset="utf-8" From: Frederic Weisbecker During the early boot process, the default clocksource used for timekeeping is the jiffies. Better clocksources can only be selected once clocksource_done_booting() is called as an fs initcall. NOHZ can only be enabled after that stage, making global timer migration irrelevant up to that point. Therefore, don't bother with trashing the cache within that tree from the SMP bootup until NOHZ even matters. Make the CPUs available to the tree on late initcall, after the right clocksource had a chance to be selected. This will also simplify the handling of domain isolated CPUs on further patches. Signed-off-by: Frederic Weisbecker Signed-off-by: Gabriele Monaco --- kernel/time/timer_migration.c | 24 +++++++++++++----------- 1 file changed, 13 insertions(+), 11 deletions(-) diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c index 2f6330831f08..72987f0d101b 100644 --- a/kernel/time/timer_migration.c +++ b/kernel/time/timer_migration.c @@ -1484,6 +1484,16 @@ static int tmigr_cpu_online(unsigned int cpu) return 0; } =20 +/* + * NOHZ can only be enabled after clocksource_done_booting(). Don't + * bother trashing the cache in the tree before. + */ +static int __init tmigr_late_init(void) +{ + return cpuhp_setup_state(CPUHP_AP_TMIGR_ONLINE, "tmigr:online", + tmigr_cpu_online, tmigr_cpu_offline); +} + static void tmigr_init_group(struct tmigr_group *group, unsigned int lvl, int node) { @@ -1846,18 +1856,10 @@ static int __init tmigr_init(void) =20 ret =3D cpuhp_setup_state(CPUHP_TMIGR_PREPARE, "tmigr:prepare", tmigr_cpu_prepare, NULL); - if (ret) - goto err; - - ret =3D cpuhp_setup_state(CPUHP_AP_TMIGR_ONLINE, "tmigr:online", - tmigr_cpu_online, tmigr_cpu_offline); - if (ret) - goto err; - - return 0; - err: - pr_err("Timer migration setup failed\n"); + if (ret) + pr_err("Timer migration setup failed\n"); return ret; } early_initcall(tmigr_init); +late_initcall(tmigr_late_init); --=20 2.50.1 From nobody Sun Oct 5 20:15:19 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 65E2B29A32D for ; Wed, 30 Jul 2025 13:12:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753881142; cv=none; b=K7GmLX2/urggjFstfaNyMvD+NWfseZQ/3Nujq+lGktVIh9wJ880Am63/pkQGAYQqCP4b4COYv1rAgrIPqcBkSvI1G7VmSsoNyzJG9/zq7sJTlrqgCcbVvJ0aFTY5m0WoknIgw69sisiK3iKps6vdkxWTg7bfRoVo6QqMsGLRx9A= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753881142; c=relaxed/simple; bh=0HScwkLmQ3+y9/9PbobCJ0NQMOASsFp4tZHU1uipZ7Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=PQPs1cGye5y7UPtq4XqmIsPB2HZB5rCauKrN33VwzCGl50+pJM5JQ3UUmGUnZdyy/Od62ymJuPu2mdxfgGrarLimCCEoPeT1iNwGUgVkiaQ1GEoGXVsBmjnOJVYaNMmL0NGMnz+5bx+A38uD2jFy/lBv8EMr88uJjWBL+AzkhAA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=f95HhJ8I; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="f95HhJ8I" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1753881139; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=dKwnncwTrJNBHrE6aUUl9sCgAqeFvNo+65VYGmZfFeM=; b=f95HhJ8IFxdUcQdBRWrZuqJMwWO36/xsNEXFDsATjAjHL5H26DRN6p/tG5R4WDRKAfWmJt PF+aYXJv8RfUvWBiuuAqDpRYwHP/3ODwbsUnlCG/R81YuEWlH2mwJ/Upr+J8iOUcKoDcGu KWXditXhHQN6FDmWAnl/jS5UerxNlVU= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-175-aImZxa92OdmdMRPbAO4UfQ-1; Wed, 30 Jul 2025 09:12:16 -0400 X-MC-Unique: aImZxa92OdmdMRPbAO4UfQ-1 X-Mimecast-MFC-AGG-ID: aImZxa92OdmdMRPbAO4UfQ_1753881136 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id D4F92180034A; Wed, 30 Jul 2025 13:12:15 +0000 (UTC) Received: from gmonaco-thinkpadt14gen3.rmtit.com (unknown [10.44.33.26]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 4DBD919560A2; Wed, 30 Jul 2025 13:12:10 +0000 (UTC) From: Gabriele Monaco To: linux-kernel@vger.kernel.org, Anna-Maria Behnsen , Frederic Weisbecker , Thomas Gleixner , Waiman Long Cc: Gabriele Monaco Subject: [PATCH v9 2/8] timers: Rename tmigr 'online' bit to 'available' Date: Wed, 30 Jul 2025 15:11:52 +0200 Message-ID: <20250730131158.101668-3-gmonaco@redhat.com> In-Reply-To: <20250730131158.101668-1-gmonaco@redhat.com> References: <20250730131158.101668-1-gmonaco@redhat.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 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Content-Type: text/plain; charset="utf-8" The timer migration hierarchy excludes offline CPUs via the tmigr_is_not_available function, which is essentially checking the online bit for the CPU. Rename the online bit to available and all references in function names and tracepoint to generalise the concept of available CPUs. Reviewed-by: Frederic Weisbecker Signed-off-by: Gabriele Monaco --- include/trace/events/timer_migration.h | 4 ++-- kernel/time/timer_migration.c | 22 +++++++++++----------- kernel/time/timer_migration.h | 2 +- 3 files changed, 14 insertions(+), 14 deletions(-) diff --git a/include/trace/events/timer_migration.h b/include/trace/events/= timer_migration.h index 47db5eaf2f9a..61171b13c687 100644 --- a/include/trace/events/timer_migration.h +++ b/include/trace/events/timer_migration.h @@ -173,14 +173,14 @@ DEFINE_EVENT(tmigr_cpugroup, tmigr_cpu_active, TP_ARGS(tmc) ); =20 -DEFINE_EVENT(tmigr_cpugroup, tmigr_cpu_online, +DEFINE_EVENT(tmigr_cpugroup, tmigr_cpu_available, =20 TP_PROTO(struct tmigr_cpu *tmc), =20 TP_ARGS(tmc) ); =20 -DEFINE_EVENT(tmigr_cpugroup, tmigr_cpu_offline, +DEFINE_EVENT(tmigr_cpugroup, tmigr_cpu_unavailable, =20 TP_PROTO(struct tmigr_cpu *tmc), =20 diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c index 72987f0d101b..75fce6b8b642 100644 --- a/kernel/time/timer_migration.c +++ b/kernel/time/timer_migration.c @@ -427,7 +427,7 @@ static DEFINE_PER_CPU(struct tmigr_cpu, tmigr_cpu); =20 static inline bool tmigr_is_not_available(struct tmigr_cpu *tmc) { - return !(tmc->tmgroup && tmc->online); + return !(tmc->tmgroup && tmc->available); } =20 /* @@ -926,7 +926,7 @@ static void tmigr_handle_remote_cpu(unsigned int cpu, u= 64 now, * updated the event takes care when hierarchy is completely * idle. Otherwise the migrator does it as the event is enqueued. */ - if (!tmc->online || tmc->remote || tmc->cpuevt.ignore || + if (!tmc->available || tmc->remote || tmc->cpuevt.ignore || now < tmc->cpuevt.nextevt.expires) { raw_spin_unlock_irq(&tmc->lock); return; @@ -973,7 +973,7 @@ static void tmigr_handle_remote_cpu(unsigned int cpu, u= 64 now, * (See also section "Required event and timerqueue update after a * remote expiry" in the documentation at the top) */ - if (!tmc->online || !tmc->idle) { + if (!tmc->available || !tmc->idle) { timer_unlock_remote_bases(cpu); goto unlock; } @@ -1435,19 +1435,19 @@ static long tmigr_trigger_active(void *unused) { struct tmigr_cpu *tmc =3D this_cpu_ptr(&tmigr_cpu); =20 - WARN_ON_ONCE(!tmc->online || tmc->idle); + WARN_ON_ONCE(!tmc->available || tmc->idle); =20 return 0; } =20 -static int tmigr_cpu_offline(unsigned int cpu) +static int tmigr_clear_cpu_available(unsigned int cpu) { struct tmigr_cpu *tmc =3D this_cpu_ptr(&tmigr_cpu); int migrator; u64 firstexp; =20 raw_spin_lock_irq(&tmc->lock); - tmc->online =3D false; + tmc->available =3D false; WRITE_ONCE(tmc->wakeup, KTIME_MAX); =20 /* @@ -1455,7 +1455,7 @@ static int tmigr_cpu_offline(unsigned int cpu) * offline; Therefore nextevt value is set to KTIME_MAX */ firstexp =3D __tmigr_cpu_deactivate(tmc, KTIME_MAX); - trace_tmigr_cpu_offline(tmc); + trace_tmigr_cpu_unavailable(tmc); raw_spin_unlock_irq(&tmc->lock); =20 if (firstexp !=3D KTIME_MAX) { @@ -1466,7 +1466,7 @@ static int tmigr_cpu_offline(unsigned int cpu) return 0; } =20 -static int tmigr_cpu_online(unsigned int cpu) +static int tmigr_set_cpu_available(unsigned int cpu) { struct tmigr_cpu *tmc =3D this_cpu_ptr(&tmigr_cpu); =20 @@ -1475,11 +1475,11 @@ static int tmigr_cpu_online(unsigned int cpu) return -EINVAL; =20 raw_spin_lock_irq(&tmc->lock); - trace_tmigr_cpu_online(tmc); + trace_tmigr_cpu_available(tmc); tmc->idle =3D timer_base_is_idle(); if (!tmc->idle) __tmigr_cpu_activate(tmc); - tmc->online =3D true; + tmc->available =3D true; raw_spin_unlock_irq(&tmc->lock); return 0; } @@ -1491,7 +1491,7 @@ static int tmigr_cpu_online(unsigned int cpu) static int __init tmigr_late_init(void) { return cpuhp_setup_state(CPUHP_AP_TMIGR_ONLINE, "tmigr:online", - tmigr_cpu_online, tmigr_cpu_offline); + tmigr_set_cpu_available, tmigr_clear_cpu_available); } =20 static void tmigr_init_group(struct tmigr_group *group, unsigned int lvl, diff --git a/kernel/time/timer_migration.h b/kernel/time/timer_migration.h index ae19f70f8170..70879cde6fdd 100644 --- a/kernel/time/timer_migration.h +++ b/kernel/time/timer_migration.h @@ -97,7 +97,7 @@ struct tmigr_group { */ struct tmigr_cpu { raw_spinlock_t lock; - bool online; + bool available; bool idle; bool remote; struct tmigr_group *tmgroup; --=20 2.50.1 From nobody Sun Oct 5 20:15:19 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 ACBF7298CDE for ; 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Wed, 30 Jul 2025 09:12:22 -0400 X-MC-Unique: KgZlg0-LOYey-cxs_dsX6g-1 X-Mimecast-MFC-AGG-ID: KgZlg0-LOYey-cxs_dsX6g_1753881141 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 6C40819560BA; Wed, 30 Jul 2025 13:12:21 +0000 (UTC) Received: from gmonaco-thinkpadt14gen3.rmtit.com (unknown [10.44.33.26]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 0D29619560A2; Wed, 30 Jul 2025 13:12:16 +0000 (UTC) From: Gabriele Monaco To: linux-kernel@vger.kernel.org, Anna-Maria Behnsen , Frederic Weisbecker , Thomas Gleixner , Waiman Long Cc: Gabriele Monaco Subject: [PATCH v9 3/8] timers: Add the available mask in timer migration Date: Wed, 30 Jul 2025 15:11:53 +0200 Message-ID: <20250730131158.101668-4-gmonaco@redhat.com> In-Reply-To: <20250730131158.101668-1-gmonaco@redhat.com> References: <20250730131158.101668-1-gmonaco@redhat.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 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Content-Type: text/plain; charset="utf-8" Keep track of the CPUs available for timer migration in a cpumask. This prepares the ground to generalise the concept of unavailable CPUs. Reviewed-by: Frederic Weisbecker Signed-off-by: Gabriele Monaco --- kernel/time/timer_migration.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c index 75fce6b8b642..57abdef7d0f8 100644 --- a/kernel/time/timer_migration.c +++ b/kernel/time/timer_migration.c @@ -422,6 +422,12 @@ static unsigned int tmigr_crossnode_level __read_mostl= y; =20 static DEFINE_PER_CPU(struct tmigr_cpu, tmigr_cpu); =20 +/* + * CPUs available for timer migration. + * Protected by cpuset_mutex (with cpus_read_lock held) or cpus_write_lock. + */ +static cpumask_var_t tmigr_available_cpumask; + #define TMIGR_NONE 0xFF #define BIT_CNT 8 =20 @@ -1446,6 +1452,7 @@ static int tmigr_clear_cpu_available(unsigned int cpu) int migrator; u64 firstexp; =20 + cpumask_clear_cpu(cpu, tmigr_available_cpumask); raw_spin_lock_irq(&tmc->lock); tmc->available =3D false; WRITE_ONCE(tmc->wakeup, KTIME_MAX); @@ -1459,7 +1466,7 @@ static int tmigr_clear_cpu_available(unsigned int cpu) raw_spin_unlock_irq(&tmc->lock); =20 if (firstexp !=3D KTIME_MAX) { - migrator =3D cpumask_any_but(cpu_online_mask, cpu); + migrator =3D cpumask_any(tmigr_available_cpumask); work_on_cpu(migrator, tmigr_trigger_active, NULL); } =20 @@ -1474,6 +1481,7 @@ static int tmigr_set_cpu_available(unsigned int cpu) if (WARN_ON_ONCE(!tmc->tmgroup)) return -EINVAL; =20 + cpumask_set_cpu(cpu, tmigr_available_cpumask); raw_spin_lock_irq(&tmc->lock); trace_tmigr_cpu_available(tmc); tmc->idle =3D timer_base_is_idle(); @@ -1811,6 +1819,11 @@ static int __init tmigr_init(void) if (ncpus =3D=3D 1) return 0; =20 + if (!zalloc_cpumask_var(&tmigr_available_cpumask, GFP_KERNEL)) { + ret =3D -ENOMEM; + goto err; + } + /* * Calculate the required hierarchy levels. Unfortunately there is no * reliable information available, unless all possible CPUs have been --=20 2.50.1 From nobody Sun Oct 5 20:15:19 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 1A1FC298987 for ; Wed, 30 Jul 2025 13:12:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753881149; cv=none; b=ESHA1V27BtACTyw+tXOQLqLuOuEX76kSzSqugcA/S1PK4HLaEODlkA8aBBSkSOPdhF0ON2gh2mc4mzsXKMObMtCX0o9KCO0a+jxzBE4yqtWW+UWhs9A2PnXG9WMtwy96qj/+nuLzOvmDk9Kjr7ZDt3tuiNqQ6fQ7lRflctuE2PU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753881149; c=relaxed/simple; bh=BS3ySg0mBW7E6/RTvIrpHJNhD38uGFfTvbx5bxYRNos=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=HV1NzCcMemqRh0/ZHjJnRm+jgMMcOhsHksUHVZ0KUReTFu4zHRXmNw9t2hApAo7114flxLDcEc/6wMotqHvVZ43BruTxYxsNRrLQYDRoSy+4t/6U7f6fKpfZQLoMrZi6LS7g9Njn/sM35ITj38Qer/3w9S8XcY4Ri7Sai9htM5E= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=CxVBk9AZ; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="CxVBk9AZ" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1753881147; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=4QNhru3mCOwLI7ftBk1RkkcO9EVRYRaVXe0cAWR0Vds=; b=CxVBk9AZfh/HRR8E23zZVtVZY028eWYKPfyoP5lxYrmjJwC+/IGMLL5pPT8snaIZg25ucP V0eZjqFwFqhbAZOaUAC3AGEvIXw+I0CX04k5vcEvpq0haHEZWsDtz67XuIlSol9z5FcK4I Wh128tQPqtRCtXz4NX6mHqc+wco+eZU= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-481-IV4WiupvN56z_qfCXRK9og-1; Wed, 30 Jul 2025 09:12:25 -0400 X-MC-Unique: IV4WiupvN56z_qfCXRK9og-1 X-Mimecast-MFC-AGG-ID: IV4WiupvN56z_qfCXRK9og_1753881144 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id A3F5819560B3; Wed, 30 Jul 2025 13:12:24 +0000 (UTC) Received: from gmonaco-thinkpadt14gen3.rmtit.com (unknown [10.44.33.26]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 0A5BC19560A2; Wed, 30 Jul 2025 13:12:21 +0000 (UTC) From: Gabriele Monaco To: linux-kernel@vger.kernel.org, Anna-Maria Behnsen , Frederic Weisbecker , Thomas Gleixner , Waiman Long Cc: Gabriele Monaco Subject: [PATCH v9 4/8] timers: Use scoped_guard when setting/clearing the tmigr available flag Date: Wed, 30 Jul 2025 15:11:54 +0200 Message-ID: <20250730131158.101668-5-gmonaco@redhat.com> In-Reply-To: <20250730131158.101668-1-gmonaco@redhat.com> References: <20250730131158.101668-1-gmonaco@redhat.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 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Content-Type: text/plain; charset="utf-8" Cleanup tmigr_clear_cpu_available() and tmigr_set_cpu_available() to prepare for easier checks on the available flag. Reviewed-by: Frederic Weisbecker Signed-off-by: Gabriele Monaco --- kernel/time/timer_migration.c | 34 +++++++++++++++++----------------- 1 file changed, 17 insertions(+), 17 deletions(-) diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c index 57abdef7d0f8..36e7f784ec60 100644 --- a/kernel/time/timer_migration.c +++ b/kernel/time/timer_migration.c @@ -1453,17 +1453,17 @@ static int tmigr_clear_cpu_available(unsigned int c= pu) u64 firstexp; =20 cpumask_clear_cpu(cpu, tmigr_available_cpumask); - raw_spin_lock_irq(&tmc->lock); - tmc->available =3D false; - WRITE_ONCE(tmc->wakeup, KTIME_MAX); + scoped_guard(raw_spinlock_irq, &tmc->lock) { + tmc->available =3D false; + WRITE_ONCE(tmc->wakeup, KTIME_MAX); =20 - /* - * CPU has to handle the local events on his own, when on the way to - * offline; Therefore nextevt value is set to KTIME_MAX - */ - firstexp =3D __tmigr_cpu_deactivate(tmc, KTIME_MAX); - trace_tmigr_cpu_unavailable(tmc); - raw_spin_unlock_irq(&tmc->lock); + /* + * CPU has to handle the local events on his own, when on the way to + * offline; Therefore nextevt value is set to KTIME_MAX + */ + firstexp =3D __tmigr_cpu_deactivate(tmc, KTIME_MAX); + trace_tmigr_cpu_unavailable(tmc); + } =20 if (firstexp !=3D KTIME_MAX) { migrator =3D cpumask_any(tmigr_available_cpumask); @@ -1482,13 +1482,13 @@ static int tmigr_set_cpu_available(unsigned int cpu) return -EINVAL; =20 cpumask_set_cpu(cpu, tmigr_available_cpumask); - raw_spin_lock_irq(&tmc->lock); - trace_tmigr_cpu_available(tmc); - tmc->idle =3D timer_base_is_idle(); - if (!tmc->idle) - __tmigr_cpu_activate(tmc); - tmc->available =3D true; - raw_spin_unlock_irq(&tmc->lock); + scoped_guard(raw_spinlock_irq, &tmc->lock) { + trace_tmigr_cpu_available(tmc); + tmc->idle =3D timer_base_is_idle(); + if (!tmc->idle) + __tmigr_cpu_activate(tmc); + tmc->available =3D true; + } return 0; } =20 --=20 2.50.1 From nobody Sun Oct 5 20:15:19 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 02997298987 for ; 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charset="utf-8" update_unbound_workqueue_cpumask() updates unbound workqueues settings when there's a change in isolated CPUs, but it can be used for other subsystems requiring updated when isolated CPUs change. Generalise the name to update_exclusion_cpumasks() to prepare for other functions unrelated to workqueues to be called in that spot. Acked-by: Frederic Weisbecker Signed-off-by: Gabriele Monaco Acked-by: Waiman Long --- kernel/cgroup/cpuset.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 3bc4301466f3..6e3f44ffaa21 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1339,7 +1339,7 @@ static bool partition_xcpus_del(int old_prs, struct c= puset *parent, return isolcpus_updated; } =20 -static void update_unbound_workqueue_cpumask(bool isolcpus_updated) +static void update_exclusion_cpumasks(bool isolcpus_updated) { int ret; =20 @@ -1470,7 +1470,7 @@ static int remote_partition_enable(struct cpuset *cs,= int new_prs, list_add(&cs->remote_sibling, &remote_children); cpumask_copy(cs->effective_xcpus, tmp->new_cpus); spin_unlock_irq(&callback_lock); - update_unbound_workqueue_cpumask(isolcpus_updated); + update_exclusion_cpumasks(isolcpus_updated); cpuset_force_rebuild(); cs->prs_err =3D 0; =20 @@ -1511,7 +1511,7 @@ static void remote_partition_disable(struct cpuset *c= s, struct tmpmasks *tmp) compute_effective_exclusive_cpumask(cs, NULL, NULL); reset_partition_data(cs); spin_unlock_irq(&callback_lock); - update_unbound_workqueue_cpumask(isolcpus_updated); + update_exclusion_cpumasks(isolcpus_updated); cpuset_force_rebuild(); =20 /* @@ -1580,7 +1580,7 @@ static void remote_cpus_update(struct cpuset *cs, str= uct cpumask *xcpus, if (xcpus) cpumask_copy(cs->exclusive_cpus, xcpus); spin_unlock_irq(&callback_lock); - update_unbound_workqueue_cpumask(isolcpus_updated); + update_exclusion_cpumasks(isolcpus_updated); if (adding || deleting) cpuset_force_rebuild(); =20 @@ -1943,7 +1943,7 @@ static int update_parent_effective_cpumask(struct cpu= set *cs, int cmd, WARN_ON_ONCE(parent->nr_subparts < 0); } spin_unlock_irq(&callback_lock); - update_unbound_workqueue_cpumask(isolcpus_updated); + update_exclusion_cpumasks(isolcpus_updated); =20 if ((old_prs !=3D new_prs) && (cmd =3D=3D partcmd_update)) update_partition_exclusive_flag(cs, new_prs); @@ -2968,7 +2968,7 @@ static int update_prstate(struct cpuset *cs, int new_= prs) else if (isolcpus_updated) isolated_cpus_update(old_prs, new_prs, cs->effective_xcpus); 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Wed, 30 Jul 2025 13:12:31 +0000 (UTC) Received: from gmonaco-thinkpadt14gen3.rmtit.com (unknown [10.44.33.26]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id ECA3419560A2; Wed, 30 Jul 2025 13:12:28 +0000 (UTC) From: Gabriele Monaco To: linux-kernel@vger.kernel.org, Anna-Maria Behnsen , Frederic Weisbecker , Thomas Gleixner , Waiman Long Cc: Gabriele Monaco Subject: [PATCH v9 6/8] sched/isolation: Force housekeeping if isolcpus and nohz_full don't leave any Date: Wed, 30 Jul 2025 15:11:56 +0200 Message-ID: <20250730131158.101668-7-gmonaco@redhat.com> In-Reply-To: <20250730131158.101668-1-gmonaco@redhat.com> References: <20250730131158.101668-1-gmonaco@redhat.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 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Content-Type: text/plain; charset="utf-8" Currently the user can set up isolcpus and nohz_full in such a way that leaves no housekeeping CPU (i.e. no CPU that is neither domain isolated nor nohz full). This can be a problem for other subsystems (e.g. the timer wheel imgration). Prevent this configuration by invalidating the last setting in case the union of isolcpus and nohz_full covers all CPUs. Reviewed-by: Frederic Weisbecker Signed-off-by: Gabriele Monaco --- kernel/sched/isolation.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c index 93b038d48900..0019d941de68 100644 --- a/kernel/sched/isolation.c +++ b/kernel/sched/isolation.c @@ -165,6 +165,18 @@ static int __init housekeeping_setup(char *str, unsign= ed long flags) } } =20 + /* Check in combination with the previously set cpumask */ + type =3D find_first_bit(&housekeeping.flags, HK_TYPE_MAX); + first_cpu =3D cpumask_first_and_and(cpu_present_mask, + housekeeping_staging, + housekeeping.cpumasks[type]); + if (first_cpu >=3D nr_cpu_ids || first_cpu >=3D setup_max_cpus) { + pr_warn("Housekeeping: must include one present CPU neither " + "in nohz_full=3D nor in isolcpus=3D, ignoring setting %s\n", + str); + goto free_housekeeping_staging; + } + iter_flags =3D flags & ~housekeeping.flags; =20 for_each_set_bit(type, &iter_flags, HK_TYPE_MAX) --=20 2.50.1 From nobody Sun Oct 5 20:15:19 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 3A9F329B22D for ; 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Wed, 30 Jul 2025 09:12:36 -0400 X-MC-Unique: byCJidUQMAOf824vbRuURg-1 X-Mimecast-MFC-AGG-ID: byCJidUQMAOf824vbRuURg_1753881155 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 9BE9019560AD; Wed, 30 Jul 2025 13:12:35 +0000 (UTC) Received: from gmonaco-thinkpadt14gen3.rmtit.com (unknown [10.44.33.26]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 9C63219560A2; Wed, 30 Jul 2025 13:12:32 +0000 (UTC) From: Gabriele Monaco To: linux-kernel@vger.kernel.org, Anna-Maria Behnsen , Frederic Weisbecker , Thomas Gleixner , Waiman Long Cc: Gabriele Monaco Subject: [PATCH v9 7/8] cgroup/cpuset: Fail if isolated and nohz_full don't leave any housekeeping Date: Wed, 30 Jul 2025 15:11:57 +0200 Message-ID: <20250730131158.101668-8-gmonaco@redhat.com> In-Reply-To: <20250730131158.101668-1-gmonaco@redhat.com> References: <20250730131158.101668-1-gmonaco@redhat.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 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Content-Type: text/plain; charset="utf-8" Currently the user can set up isolated cpus via cpuset and nohz_full in such a way that leaves no housekeeping CPU (i.e. no CPU that is neither domain isolated nor nohz full). This can be a problem for other subsystems (e.g. the timer wheel imgration). Prevent this configuration by blocking any assignation that would cause the union of domain isolated cpus and nohz_full to covers all CPUs. Acked-by: Frederic Weisbecker Signed-off-by: Gabriele Monaco --- kernel/cgroup/cpuset.c | 56 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 56 insertions(+) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 6e3f44ffaa21..a946d85ce954 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1275,6 +1275,19 @@ static void isolated_cpus_update(int old_prs, int ne= w_prs, struct cpumask *xcpus cpumask_andnot(isolated_cpus, isolated_cpus, xcpus); } =20 +/* + * isolated_cpus_should_update - Returns if the isolated_cpus mask needs u= pdate + * @prs: new or old partition_root_state + * @parent: parent cpuset + * Return: true if isolated_cpus needs modification, false otherwise + */ +static bool isolated_cpus_should_update(int prs, struct cpuset *parent) +{ + if (!parent) + parent =3D &top_cpuset; + return prs !=3D parent->partition_root_state; +} + /* * partition_xcpus_add - Add new exclusive CPUs to partition * @new_prs: new partition_root_state @@ -1339,6 +1352,35 @@ static bool partition_xcpus_del(int old_prs, struct = cpuset *parent, return isolcpus_updated; } =20 +/* + * isolcpus_nohz_conflict - check for isolated & nohz_full conflicts + * @new_cpus: cpu mask for cpus that are going to be isolated + * Return: true if there is conflict, false otherwise + * + * If nohz_full is enabled and we have isolated CPUs, their combination mu= st + * still leave housekeeping CPUs. + */ +static bool isolcpus_nohz_conflict(struct cpumask *new_cpus) +{ + cpumask_var_t full_hk_cpus; + int res =3D false; + + if (!housekeeping_enabled(HK_TYPE_KERNEL_NOISE)) + return false; + + if (!alloc_cpumask_var(&full_hk_cpus, GFP_KERNEL)) + return true; + + cpumask_and(full_hk_cpus, housekeeping_cpumask(HK_TYPE_KERNEL_NOISE), + housekeeping_cpumask(HK_TYPE_DOMAIN)); + cpumask_and(full_hk_cpus, full_hk_cpus, cpu_online_mask); + if (!cpumask_weight_andnot(full_hk_cpus, new_cpus)) + res =3D true; + + free_cpumask_var(full_hk_cpus); + return res; +} + static void update_exclusion_cpumasks(bool isolcpus_updated) { int ret; @@ -1464,6 +1506,9 @@ static int remote_partition_enable(struct cpuset *cs,= int new_prs, if (!cpumask_intersects(tmp->new_cpus, cpu_active_mask) || cpumask_subset(top_cpuset.effective_cpus, tmp->new_cpus)) return PERR_INVCPUS; + if (isolated_cpus_should_update(new_prs, NULL) && + isolcpus_nohz_conflict(tmp->new_cpus)) + return PERR_HKEEPING; =20 spin_lock_irq(&callback_lock); isolcpus_updated =3D partition_xcpus_add(new_prs, NULL, tmp->new_cpus); @@ -1563,6 +1608,9 @@ static void remote_cpus_update(struct cpuset *cs, str= uct cpumask *xcpus, else if (cpumask_intersects(tmp->addmask, subpartitions_cpus) || cpumask_subset(top_cpuset.effective_cpus, tmp->addmask)) cs->prs_err =3D PERR_NOCPUS; + else if (isolated_cpus_should_update(prs, NULL) && + isolcpus_nohz_conflict(tmp->addmask)) + cs->prs_err =3D PERR_HKEEPING; if (cs->prs_err) goto invalidate; } @@ -1914,6 +1962,12 @@ static int update_parent_effective_cpumask(struct cp= uset *cs, int cmd, return err; } =20 + if (deleting && isolated_cpus_should_update(new_prs, parent) && + isolcpus_nohz_conflict(tmp->delmask)) { + cs->prs_err =3D PERR_HKEEPING; + return PERR_HKEEPING; + } + /* * Change the parent's effective_cpus & effective_xcpus (top cpuset * only). @@ -2934,6 +2988,8 @@ static int update_prstate(struct cpuset *cs, int new_= prs) * Need to update isolated_cpus. */ isolcpus_updated =3D true; 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Wed, 30 Jul 2025 13:12:38 +0000 (UTC) Received: from gmonaco-thinkpadt14gen3.rmtit.com (unknown [10.44.33.26]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 3A9FB19560A2; Wed, 30 Jul 2025 13:12:35 +0000 (UTC) From: Gabriele Monaco To: linux-kernel@vger.kernel.org, Anna-Maria Behnsen , Frederic Weisbecker , Thomas Gleixner , Waiman Long Cc: Gabriele Monaco Subject: [PATCH v9 8/8] timers: Exclude isolated cpus from timer migration Date: Wed, 30 Jul 2025 15:11:58 +0200 Message-ID: <20250730131158.101668-9-gmonaco@redhat.com> In-Reply-To: <20250730131158.101668-1-gmonaco@redhat.com> References: <20250730131158.101668-1-gmonaco@redhat.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 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Content-Type: text/plain; charset="utf-8" The timer migration mechanism allows active CPUs to pull timers from idle ones to improve the overall idle time. This is however undesired when CPU intensive workloads run on isolated cores, as the algorithm would move the timers from housekeeping to isolated cores, negatively affecting the isolation. Exclude isolated cores from the timer migration algorithm, extend the concept of unavailable cores, currently used for offline ones, to isolated ones: * A core is unavailable if isolated or offline; * A core is available if non isolated and online; A core is considered unavailable as isolated if it belongs to: * the isolcpus (domain) list * an isolated cpuset Except if it is: * in the nohz_full list (already idle for the hierarchy) * the nohz timekeeper core (must be available to handle global timers) CPUs are added to the hierarchy during late boot, excluding isolated ones, the hierarchy is also adapted when the cpuset isolation changes. Due to how the timer migration algorithm works, any CPU part of the hierarchy can have their global timers pulled by remote CPUs and have to pull remote timers, only skipping pulling remote timers would break the logic. For this reason, prevent isolated CPUs from pulling remote global timers, but also the other way around: any global timer started on an isolated CPU will run there. This does not break the concept of isolation (global timers don't come from outside the CPU) and, if considered inappropriate, can usually be mitigated with other isolation techniques (e.g. IRQ pinning). This effect was noticed on a 128 cores machine running oslat on the isolated cores (1-31,33-63,65-95,97-127). The tool monopolises CPUs, and the CPU with lowest count in a timer migration hierarchy (here 1 and 65) appears as always active and continuously pulls global timers, from the housekeeping CPUs. This ends up moving driver work (e.g. delayed work) to isolated CPUs and causes latency spikes: before the change: # oslat -c 1-31,33-63,65-95,97-127 -D 62s ... Maximum: 1203 10 3 4 ... 5 (us) after the change: # oslat -c 1-31,33-63,65-95,97-127 -D 62s ... Maximum: 10 4 3 4 3 ... 5 (us) Signed-off-by: Gabriele Monaco --- include/linux/timer.h | 9 +++ kernel/cgroup/cpuset.c | 3 + kernel/time/timer_migration.c | 100 +++++++++++++++++++++++++++++++++- 3 files changed, 109 insertions(+), 3 deletions(-) diff --git a/include/linux/timer.h b/include/linux/timer.h index 0414d9e6b4fc..62e1cea71125 100644 --- a/include/linux/timer.h +++ b/include/linux/timer.h @@ -188,4 +188,13 @@ int timers_dead_cpu(unsigned int cpu); #define timers_dead_cpu NULL #endif =20 +#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON) +extern int tmigr_isolated_exclude_cpumask(struct cpumask *exclude_cpumask); +#else +static inline int tmigr_isolated_exclude_cpumask(struct cpumask *exclude_c= pumask) +{ + return 0; +} +#endif + #endif diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index a946d85ce954..ff5b66abd047 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1392,6 +1392,9 @@ static void update_exclusion_cpumasks(bool isolcpus_u= pdated) =20 ret =3D workqueue_unbound_exclude_cpumask(isolated_cpus); WARN_ON_ONCE(ret < 0); + + ret =3D tmigr_isolated_exclude_cpumask(isolated_cpus); + WARN_ON_ONCE(ret < 0); } =20 /** diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c index 36e7f784ec60..5e66147fce11 100644 --- a/kernel/time/timer_migration.c +++ b/kernel/time/timer_migration.c @@ -10,6 +10,7 @@ #include #include #include +#include =20 #include "timer_migration.h" #include "tick-internal.h" @@ -436,6 +437,20 @@ static inline bool tmigr_is_not_available(struct tmigr= _cpu *tmc) return !(tmc->tmgroup && tmc->available); } =20 +/* + * Returns true if @cpu should be excluded from the hierarchy as isolated. + * Domain isolated CPUs don't participate in timer migration, nohz_full + * CPUs are still part of the hierarchy but are always considered idle. + * This check is necessary, for instance, to prevent offline isolated CPU = from + * being incorrectly marked as available once getting back online. + */ +static inline bool tmigr_is_isolated(int cpu) +{ + return (!housekeeping_cpu(cpu, HK_TYPE_DOMAIN) || + cpuset_cpu_is_isolated(cpu)) && + housekeeping_cpu(cpu, HK_TYPE_KERNEL_NOISE); +} + /* * Returns true, when @childmask corresponds to the group migrator or when= the * group is not active - so no migrator is set. @@ -1454,6 +1469,8 @@ static int tmigr_clear_cpu_available(unsigned int cpu) =20 cpumask_clear_cpu(cpu, tmigr_available_cpumask); scoped_guard(raw_spinlock_irq, &tmc->lock) { + if (!tmc->available) + return 0; tmc->available =3D false; WRITE_ONCE(tmc->wakeup, KTIME_MAX); =20 @@ -1473,7 +1490,7 @@ static int tmigr_clear_cpu_available(unsigned int cpu) return 0; } =20 -static int tmigr_set_cpu_available(unsigned int cpu) +static inline int _tmigr_set_cpu_available(unsigned int cpu) { struct tmigr_cpu *tmc =3D this_cpu_ptr(&tmigr_cpu); =20 @@ -1483,6 +1500,8 @@ static int tmigr_set_cpu_available(unsigned int cpu) =20 cpumask_set_cpu(cpu, tmigr_available_cpumask); scoped_guard(raw_spinlock_irq, &tmc->lock) { + if (tmc->available) + return 0; trace_tmigr_cpu_available(tmc); tmc->idle =3D timer_base_is_idle(); if (!tmc->idle) @@ -1492,14 +1511,89 @@ static int tmigr_set_cpu_available(unsigned int cpu) return 0; } =20 +static int tmigr_set_cpu_available(unsigned int cpu) +{ + if (tmigr_is_isolated(cpu)) + return 0; + return _tmigr_set_cpu_available(cpu); +} + +static bool tmigr_should_isolate_cpu(int cpu, void *ignored) +{ + /* + * The tick CPU can be marked as isolated by the cpuset code, however + * we cannot mark it as unavailable to avoid having no global migrator + * for the nohz_full CPUs. + */ + return tick_nohz_cpu_hotpluggable(cpu); +} + +static void tmigr_cpu_isolate(void *ignored) +{ + tmigr_clear_cpu_available(smp_processor_id()); +} + +static void tmigr_cpu_unisolate(void *ignored) +{ + tmigr_set_cpu_available(smp_processor_id()); +} + +static void tmigr_cpu_unisolate_force(void *ignored) +{ + /* + * Required at boot to restore the tick CPU if nohz_full is available. + * Hotplug handlers don't check for tick CPUs during runtime. + */ + _tmigr_set_cpu_available(smp_processor_id()); +} + +int tmigr_isolated_exclude_cpumask(struct cpumask *exclude_cpumask) +{ + cpumask_var_t cpumask; + + lockdep_assert_cpus_held(); + + if (!alloc_cpumask_var(&cpumask, GFP_KERNEL)) + return -ENOMEM; + + cpumask_and(cpumask, exclude_cpumask, tmigr_available_cpumask); + cpumask_and(cpumask, cpumask, housekeeping_cpumask(HK_TYPE_KERNEL_NOISE)); + on_each_cpu_cond_mask(tmigr_should_isolate_cpu, tmigr_cpu_isolate, NULL, + 1, cpumask); + + cpumask_andnot(cpumask, cpu_online_mask, exclude_cpumask); + cpumask_andnot(cpumask, cpumask, tmigr_available_cpumask); + on_each_cpu_mask(cpumask, tmigr_cpu_unisolate, NULL, 1); + + free_cpumask_var(cpumask); + return 0; +} + /* * NOHZ can only be enabled after clocksource_done_booting(). Don't * bother trashing the cache in the tree before. */ static int __init tmigr_late_init(void) { - return cpuhp_setup_state(CPUHP_AP_TMIGR_ONLINE, "tmigr:online", - tmigr_set_cpu_available, tmigr_clear_cpu_available); + int cpu, ret; + + ret =3D cpuhp_setup_state(CPUHP_AP_TMIGR_ONLINE, "tmigr:online", + tmigr_set_cpu_available, tmigr_clear_cpu_available); + if (ret) + return ret; + /* + * The tick CPU may not be marked as available in the above call, this + * can occur only at boot as hotplug handlers are not called on the + * tick CPU. Force it enabled here. + */ + for_each_possible_cpu(cpu) { + if (!tick_nohz_cpu_hotpluggable(cpu)) { + ret =3D smp_call_function_single( + cpu, tmigr_cpu_unisolate_force, NULL, 1); + break; + } + } + return ret; } =20 static void tmigr_init_group(struct tmigr_group *group, unsigned int lvl, --=20 2.50.1