From nobody Mon Feb 9 17:56:32 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 9EFE72BEFF9; Mon, 3 Nov 2025 07:19:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762154354; cv=none; b=tqtGZI9/Y+17C9RWZqbyOlfgnuRSRL8iNkaEqLqN9S4aS8efEnyWMR0zGNCn5kD5XU9f4LMZru/azRF97D4bmc01OTxmUiWyfroa5Gm/LCLsFinTMezcTBt5He02gy636OdrxCdxlSqJqm3e80ZbAONKAUFqBxRP0TJRN7uapVU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762154354; c=relaxed/simple; bh=8ZCRNXXqmbiShzfe05dmFtCIZXEOypE5e1dE70Rypfo=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=SrmVUqewK4ae0LS7nEjq073MUdqDYkpOxWnzeNQFs/PECsUQTd0dqllCMB0uCJ3aRNvqdUYm/dsZVhGlFM1iKkvIG5ERC3jXEaJgFecwR+sNmfu8aTfcBUKMHFFDyYKuheTs+buL6FnCRs2fMKAPUGR62a4+72yp6MWvnYeN10U= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=uWSg0cJ3; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="uWSg0cJ3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 78A66C19423; Mon, 3 Nov 2025 07:19:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762154354; bh=8ZCRNXXqmbiShzfe05dmFtCIZXEOypE5e1dE70Rypfo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uWSg0cJ31rkYVJyjqhuAnue/g4l4rIK0s8Konh5jLRD36uxNAaFltUbqKR/ocyvNj u8UV+2QAWAWSbnKTrQrkCyu4LD+3DPPVdnsVB9CToWPEJyg6MOcvieckyqoS88BgMy 1nWfYssSxzanfQRhtW4G/QSIDtPlfbn1W3tToDx0yrZ6//SJuYMTICHXoCu4plIemz pH7d/8Ls52k3Cw7gVJl1sa0AaJgwO18qXv0RDuW/lYMsHFHRQWtkn13n9qAoOeVRWx iSnouZb7vALblJe7Txv0uGeCtBuFE4TvReUz1SKKu1HolxAAOdU82xSS5g9YXb0//y Qw3HJjINaeTqQ== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 04793CE160B; Sun, 2 Nov 2025 14:49:50 -0800 (PST) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Mathieu Desnoyers , Sebastian Andrzej Siewior , bpf@vger.kernel.org Subject: [PATCH 8/8] refscale: Add SRCU-fast-updown readers Date: Sun, 2 Nov 2025 14:49:48 -0800 Message-Id: <20251102224948.3906224-8-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <19fae851-0c49-43d2-9bbf-913424641ff4@paulmck-laptop> References: <19fae851-0c49-43d2-9bbf-913424641ff4@paulmck-laptop> 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" This commit adds refscale readers based on srcu_read_lock_fast_updown() and srcu_read_lock_fast_updown() ("refscale.scale_type=3Dsrcu-fast-updown"). On my x86 laptop, these are about 2.2ns per pair. Signed-off-by: Paul E. McKenney Cc: Mathieu Desnoyers Cc: Steven Rostedt Cc: Sebastian Andrzej Siewior Cc: --- kernel/rcu/refscale.c | 40 +++++++++++++++++++++++++++++++++++++++- 1 file changed, 39 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c index 7429ec9f0092..07a313782dfd 100644 --- a/kernel/rcu/refscale.c +++ b/kernel/rcu/refscale.c @@ -186,6 +186,7 @@ static const struct ref_scale_ops rcu_ops =3D { // Definitions for SRCU ref scale testing. DEFINE_STATIC_SRCU(srcu_refctl_scale); DEFINE_STATIC_SRCU_FAST(srcu_fast_refctl_scale); +DEFINE_STATIC_SRCU_FAST_UPDOWN(srcu_fast_updown_refctl_scale); static struct srcu_struct *srcu_ctlp =3D &srcu_refctl_scale; =20 static void srcu_ref_scale_read_section(const int nloops) @@ -254,6 +255,42 @@ static const struct ref_scale_ops srcu_fast_ops =3D { .name =3D "srcu-fast" }; =20 +static bool srcu_fast_updown_sync_scale_init(void) +{ + srcu_ctlp =3D &srcu_fast_updown_refctl_scale; + return true; +} + +static void srcu_fast_updown_ref_scale_read_section(const int nloops) +{ + int i; + struct srcu_ctr __percpu *scp; + + for (i =3D nloops; i >=3D 0; i--) { + scp =3D srcu_read_lock_fast_updown(srcu_ctlp); + srcu_read_unlock_fast_updown(srcu_ctlp, scp); + } +} + +static void srcu_fast_updown_ref_scale_delay_section(const int nloops, con= st int udl, const int ndl) +{ + int i; + struct srcu_ctr __percpu *scp; + + for (i =3D nloops; i >=3D 0; i--) { + scp =3D srcu_read_lock_fast_updown(srcu_ctlp); + un_delay(udl, ndl); + srcu_read_unlock_fast_updown(srcu_ctlp, scp); + } +} + +static const struct ref_scale_ops srcu_fast_updown_ops =3D { + .init =3D srcu_fast_updown_sync_scale_init, + .readsection =3D srcu_fast_updown_ref_scale_read_section, + .delaysection =3D srcu_fast_updown_ref_scale_delay_section, + .name =3D "srcu-fast-updown" +}; + #ifdef CONFIG_TASKS_RCU =20 // Definitions for RCU Tasks ref scale testing: Empty read markers. @@ -1479,7 +1516,8 @@ ref_scale_init(void) long i; int firsterr =3D 0; static const struct ref_scale_ops *scale_ops[] =3D { - &rcu_ops, &srcu_ops, &srcu_fast_ops, RCU_TRACE_OPS RCU_TASKS_OPS + &rcu_ops, &srcu_ops, &srcu_fast_ops, &srcu_fast_updown_ops, + RCU_TRACE_OPS RCU_TASKS_OPS &refcnt_ops, &percpuinc_ops, &incpercpu_ops, &incpercpupreempt_ops, &incpercpubh_ops, &incpercpuirqsave_ops, &rwlock_ops, &rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops, --=20 2.40.1