From nobody Thu Oct 2 03:28:36 2025 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 5EE6632951D; Tue, 23 Sep 2025 14:22:04 +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=1758637324; cv=none; b=lTMqZDnvSxqpEWsHuoxabftxRytPOn+M+ByPuNp2IOrzYV33rirnW7CJSCQ6pvpNld8M5HBSHzQVwgpAL6LaZ9Nbx7lSYagKEZRha/l5a8Kr/CYXVo3KpYLDc6hH9CP3mf7BnNnbvFtFaY42LWv7NC4lfpo1krB82nkKRMv5zYI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758637324; c=relaxed/simple; bh=/tPpaG65gLbvD7rU4GOXgMQxivskQwWOEjt2Xk9cxII=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=vCAeDdFLoJSU9rO7oIIM4A4xu8xgTQd3F9bnSuNgcXyuGaX7cjn60AN3S9QJR/88NIgXUhHu8Dy2su/pzIEPOU+CMnlYIWRR+tlBO+EuZQgklJlrfCZZNiE7glse9GFiLzS0gpGUqqtwjN2rnkPLYmsWhkVWaRQLNECH7gfDoW0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=OX4sPfBT; 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="OX4sPfBT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8C42CC113CF; Tue, 23 Sep 2025 14:22:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1758637324; bh=/tPpaG65gLbvD7rU4GOXgMQxivskQwWOEjt2Xk9cxII=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OX4sPfBTV+8CTfM3Idwl5WTLtfiK3ifO9ACtJgyVxrM7e2gOYrUIx3tS530p53tCo eHbOhfLYa0wD4/XLppz7b8P/IO4ZmcDXmPdjr6dXnykEBmegczWtE3f7WmZy94Hsf5 yjGF1ERZsszXvrweaN0nrai25TX026nu7REBV57ZV9hRT5Nb2VanXW7Nrp4OAuI98E Cny0yfPgiuHskPSoJNJ4kQ6YrVTxUuCx1UmZbxZLxLkf4bTVD6lM0EMCMCzErlUUA1 NKTxfRm+05U+96+v1DGmk+IJPcdSnZDjkwAPGe9ezY7Pj+3twSy60TdP1ahVq1CeN0 9kzS/QTm1YKpA== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id DF8EECE14C5; Tue, 23 Sep 2025 07:20:37 -0700 (PDT) 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" , Andrii Nakryiko , Alexei Starovoitov , Peter Zijlstra , bpf@vger.kernel.org Subject: [PATCH 16/34] rcu: Remove now-unused rcu_task_ipi_delay and TASKS_TRACE_RCU_READ_MB Date: Tue, 23 Sep 2025 07:20:18 -0700 Message-Id: <20250923142036.112290-16-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <580ea2de-799a-4ddc-bde9-c16f3fb1e6e7@paulmck-laptop> References: <580ea2de-799a-4ddc-bde9-c16f3fb1e6e7@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" Now that RCU Tasks Trace being defined in terms of SRCU-fast, the rcupdate.rcu_task_ipi_delay kernel boot parameter and the TASKS_TRACE_RCU_READ_MB Kconfig option are no longer used. This commit therefore removes them. Signed-off-by: Paul E. McKenney Cc: Andrii Nakryiko Cc: Alexei Starovoitov Cc: Peter Zijlstra Cc: --- .../admin-guide/kernel-parameters.txt | 7 ------- kernel/rcu/Kconfig | 18 ------------------ kernel/rcu/tasks.h | 5 ----- .../selftests/rcutorture/configs/rcu/TRACE01 | 1 - .../selftests/rcutorture/configs/rcu/TRACE02 | 1 - 5 files changed, 32 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentatio= n/admin-guide/kernel-parameters.txt index 54d31a5e46e1cf..40fc198bed4db9 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -6078,13 +6078,6 @@ dynamically) adjusted. This parameter is intended for use in testing. =20 - rcupdate.rcu_task_ipi_delay=3D [KNL] - Set time in jiffies during which RCU tasks will - avoid sending IPIs, starting with the beginning - of a given grace period. Setting a large - number avoids disturbing real-time workloads, - but lengthens grace periods. - rcupdate.rcu_task_lazy_lim=3D [KNL] Number of callbacks on a given CPU that will cancel laziness on that CPU. Use -1 to disable diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig index eeaa1cd47c6c4c..73a6cc364628b5 100644 --- a/kernel/rcu/Kconfig +++ b/kernel/rcu/Kconfig @@ -313,24 +313,6 @@ config RCU_NOCB_CPU_CB_BOOST Say Y here if you want to set RT priority for offloading kthreads. Say N here if you are building a !PREEMPT_RT kernel and are unsure. =20 -config TASKS_TRACE_RCU_READ_MB - bool "Tasks Trace RCU readers use memory barriers in user and idle" - depends on RCU_EXPERT && TASKS_TRACE_RCU - default PREEMPT_RT || NR_CPUS < 8 - help - Use this option to further reduce the number of IPIs sent - to CPUs executing in userspace or idle during tasks trace - RCU grace periods. Given that a reasonable setting of - the rcupdate.rcu_task_ipi_delay kernel boot parameter - eliminates such IPIs for many workloads, proper setting - of this Kconfig option is important mostly for aggressive - real-time installations and for battery-powered devices, - hence the default chosen above. - - Say Y here if you hate IPIs. - Say N here if you hate read-side memory barriers. - Take the default if you are unsure. - config RCU_LAZY bool "RCU callback lazy invocation functionality" depends on RCU_NOCB_CPU diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index a3c16e65e16812..833e180db744f2 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -161,11 +161,6 @@ static void tasks_rcu_exit_srcu_stall(struct timer_lis= t *unused); static DEFINE_TIMER(tasks_rcu_exit_srcu_stall_timer, tasks_rcu_exit_srcu_s= tall); #endif =20 -/* Avoid IPIing CPUs early in the grace period. */ -#define RCU_TASK_IPI_DELAY (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB) ? H= Z / 2 : 0) -static int rcu_task_ipi_delay __read_mostly =3D RCU_TASK_IPI_DELAY; -module_param(rcu_task_ipi_delay, int, 0644); - /* Control stall timeouts. Disable with <=3D 0, otherwise jiffies till st= all. */ #define RCU_TASK_BOOT_STALL_TIMEOUT (HZ * 30) #define RCU_TASK_STALL_TIMEOUT (HZ * 60 * 10) diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TRACE01 b/tools= /testing/selftests/rcutorture/configs/rcu/TRACE01 index 85b407467454a2..18efab346381a4 100644 --- a/tools/testing/selftests/rcutorture/configs/rcu/TRACE01 +++ b/tools/testing/selftests/rcutorture/configs/rcu/TRACE01 @@ -10,5 +10,4 @@ CONFIG_PROVE_LOCKING=3Dn #CHECK#CONFIG_PROVE_RCU=3Dn CONFIG_FORCE_TASKS_TRACE_RCU=3Dy #CHECK#CONFIG_TASKS_TRACE_RCU=3Dy -CONFIG_TASKS_TRACE_RCU_READ_MB=3Dy CONFIG_RCU_EXPERT=3Dy diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TRACE02 b/tools= /testing/selftests/rcutorture/configs/rcu/TRACE02 index 9003c56cd76484..8da390e8282977 100644 --- a/tools/testing/selftests/rcutorture/configs/rcu/TRACE02 +++ b/tools/testing/selftests/rcutorture/configs/rcu/TRACE02 @@ -9,6 +9,5 @@ CONFIG_PROVE_LOCKING=3Dy #CHECK#CONFIG_PROVE_RCU=3Dy CONFIG_FORCE_TASKS_TRACE_RCU=3Dy #CHECK#CONFIG_TASKS_TRACE_RCU=3Dy -CONFIG_TASKS_TRACE_RCU_READ_MB=3Dn CONFIG_RCU_EXPERT=3Dy CONFIG_DEBUG_OBJECTS=3Dy --=20 2.40.1