From patchwork Tue Feb 20 18:31:15 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Uladzislau Rezki X-Patchwork-Id: 13564341 Received: from mail-lf1-f47.google.com (mail-lf1-f47.google.com [209.85.167.47]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2F479127B76; Tue, 20 Feb 2024 18:31:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.47 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708453885; cv=none; b=ltpjKX1EywNdQ3pIkyWg3u/UgXEu4cEWQmGkwgGj11F/Z4niX5PEX60hR9eqVrHZ74ApdGdRAVwMmvMs0MyYIh81AYe2rJMRMKorF02rghjUxmLVEKAcEHocO6mjce9mW+7YH8JScilPeJ0pJlHkCWpvw0Hnu6VwGw9Jpd/KL04= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708453885; c=relaxed/simple; bh=l89RWgPz2iqTJBk3s+AeEhVE9dSu7ScUqa1mPU2DCVk=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=ezf/I9hJ5qI8CD73+efOHbqJ9UbK7ywDaZaTzbIWdOV7K/P+P7RzwVYFX2PUYaagkppFH0eTWsTyQz2ZF87+A3XX+bk3fjeop5jm3hEE9EPRCEmKB1cW0DQtOZq+sJZ0NdBVgh6Im9VZfIUGoVXY9n/+9T8WfUC0dD31ihZPKyg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=OZNAvdcl; arc=none smtp.client-ip=209.85.167.47 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="OZNAvdcl" Received: by mail-lf1-f47.google.com with SMTP id 2adb3069b0e04-512bce554a5so2601905e87.3; Tue, 20 Feb 2024 10:31:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1708453881; x=1709058681; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=6kWaBqD0vOuk8Z+fTVr0T6CR2C9b1D4p7NocTjVSfYM=; b=OZNAvdclwuQjawJ3A3KZ0sALhuWfKa3gdWtQfHGrKqX3siy60QAcK5gqoO0NVb6yP7 z0kn0cfsQuQfOxu4dK3akVvc7Vw+pEmk98SSD6cKdAS6fjyFNf1q72+LBvXs0fr5bp0l eV64SnvTJzJooAOs+/BEeuYWnWeqgphatXQUxxTlQQ0aZh8Yrc6AyHPsjDKhXpRNRRY5 qRTPShR4wg/IzFW/PLVENhJRju1Pj8s2igGFBcRnmtmgyPpw7WmkSmgIHZ5Xp9OI04Yk 4HhrPkziX53HizYmU/eIKvoMcOOhE0qKc8jM5KYtAbj5Qf50KVMHPQ+oQnfo1OcTJxrn bTGg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1708453881; x=1709058681; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=6kWaBqD0vOuk8Z+fTVr0T6CR2C9b1D4p7NocTjVSfYM=; b=Lg77LX3lM0Bbh2yqshg2YUAQmk7AqxabvtUYhqYBipNyRdu5SqWJcBuhtK2L9z7ptc 85tvvgkNvs/+rPZjJqxrhmXeDPBELGtqL2hl8kcBMO1zbMFktASoUtOpNv4GDd4R8x7J NAXlvQxQuozEB32jjaHsq+H8J9+kGNVNXiuO7ei7vy/zlK2/yo6htGsAmlHlZ8mOOc5v ubnOcZgTdR0P4cvRbJbGTs38bbY22mNdTCc9IFgxGtvLNdDWwhoyYCa89vG2b+wL+M1p keTv1IcBiefCwV+kLbjo/auedYI+rn3vdxdIdKwxoZtpEj+tMNS/8AFJLkoRM1fETjyS Jwbw== X-Forwarded-Encrypted: i=1; AJvYcCVxD5Z8EhgcqHRWLMmEMR4G5W0NtQw1Y6tKXFAodz6KnThAsQ2lb8uBQHb9G1qtlRqwGXUI1ajHVesNiY8xYN0WsTz2xdeoXNvgEZtx X-Gm-Message-State: AOJu0YyMAncnR8XmJtBO2cSV10qNflSFnQfrbPdGY6vk+uqzJRQLzGnP D8KAjFuzasLBk7WbCVn3mAbvDye2bGnoVJXfNmID1MLbiihJeACdvLje+R52 X-Google-Smtp-Source: AGHT+IEIFruNbjA6lIlRnwaNww/H4ag/9ylwKLheyLBkY8mB91yELl6eJpDS8GU14tELfL9nNLw9Lg== X-Received: by 2002:a05:6512:3c9d:b0:511:9d36:18a8 with SMTP id h29-20020a0565123c9d00b005119d3618a8mr13126055lfv.2.1708453881137; Tue, 20 Feb 2024 10:31:21 -0800 (PST) Received: from pc638.lan (host-185-121-47-193.sydskane.nu. [185.121.47.193]) by smtp.gmail.com with ESMTPSA id b14-20020ac247ee000000b005118add498asm1365937lfp.130.2024.02.20.10.31.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Feb 2024 10:31:20 -0800 (PST) From: "Uladzislau Rezki (Sony)" To: "Paul E . McKenney" Cc: RCU , Neeraj upadhyay , Boqun Feng , Hillf Danton , Joel Fernandes , LKML , Uladzislau Rezki , Oleksiy Avramchenko , Frederic Weisbecker Subject: [PATCH v5 4/4] rcu: Support direct wake-up of synchronize_rcu() users Date: Tue, 20 Feb 2024 19:31:15 +0100 Message-Id: <20240220183115.74124-5-urezki@gmail.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20240220183115.74124-1-urezki@gmail.com> References: <20240220183115.74124-1-urezki@gmail.com> Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 This patch introduces a small enhancement which allows to do a direct wake-up of synchronize_rcu() callers. It occurs after a completion of grace period, thus by the gp-kthread. Number of clients is limited by the hard-coded maximum allowed threshold. The remaining part, if still exists is deferred to a main worker. Signed-off-by: Uladzislau Rezki (Sony) --- kernel/rcu/tree.c | 31 +++++++++++++++++++++++++++++-- kernel/rcu/tree.h | 6 ++++++ 2 files changed, 35 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 3bf6b3c5ef05..31f3a61f9c38 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1644,7 +1644,8 @@ static void rcu_sr_normal_gp_cleanup_work(struct work_struct *work) */ static void rcu_sr_normal_gp_cleanup(void) { - struct llist_node *wait_tail; + struct llist_node *wait_tail, *next, *rcu; + int done = 0; wait_tail = rcu_state.srs_wait_tail; if (wait_tail == NULL) @@ -1652,12 +1653,38 @@ static void rcu_sr_normal_gp_cleanup(void) rcu_state.srs_wait_tail = NULL; ASSERT_EXCLUSIVE_WRITER(rcu_state.srs_wait_tail); + WARN_ON_ONCE(!rcu_sr_is_wait_head(wait_tail)); + + /* + * Process (a) and (d) cases. See an illustration. Apart of + * that it handles the scenario when all clients are done, + * wait-head is released if last. The worker is not kicked. + */ + llist_for_each_safe(rcu, next, wait_tail->next) { + if (rcu_sr_is_wait_head(rcu)) { + if (!rcu->next) { + rcu_sr_put_wait_head(rcu); + wait_tail->next = NULL; + } else { + wait_tail->next = rcu; + } + + break; + } + + rcu_sr_normal_complete(rcu); + // It can be last, update a next on this step. + wait_tail->next = next; + + if (++done == SR_MAX_USERS_WAKE_FROM_GP) + break; + } // concurrent sr_normal_gp_cleanup work might observe this update. smp_store_release(&rcu_state.srs_done_tail, wait_tail); ASSERT_EXCLUSIVE_WRITER(rcu_state.srs_done_tail); - if (wait_tail) + if (wait_tail->next) queue_work(system_highpri_wq, &rcu_state.srs_cleanup_work); } diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index b942b9437438..2832787cee1d 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -315,6 +315,12 @@ do { \ __set_current_state(TASK_RUNNING); \ } while (0) +/* + * A max threshold for synchronize_rcu() users which are + * awaken directly by the rcu_gp_kthread(). Left part is + * deferred to the main worker. + */ +#define SR_MAX_USERS_WAKE_FROM_GP 5 #define SR_NORMAL_GP_WAIT_HEAD_MAX 5 struct sr_wait_node {