From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B9C13C4363D for ; Thu, 24 Sep 2020 00:08:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 65B83204EC for ; Thu, 24 Sep 2020 00:08:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=mg.codeaurora.org header.i=@mg.codeaurora.org header.b="riY1GyaV" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726650AbgIXAIn (ORCPT ); Wed, 23 Sep 2020 20:08:43 -0400 Received: from m42-4.mailgun.net ([69.72.42.4]:33352 "EHLO m42-4.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726562AbgIXAIn (ORCPT ); Wed, 23 Sep 2020 20:08:43 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1600906122; h=References: In-Reply-To: Message-Id: Date: Subject: Cc: To: From: Sender; bh=eyjFT2SFuhu/vOff1LvuDvKanm9dHwCnn7IY9td+E7I=; b=riY1GyaV0J7wnQRJFMBRiR67Tnp6HjqgFZt2SqPcITsi1JLjL6H0urZM3pA39GOzepdq7Dk4 pQqN/Y+ccVM6R7mWjtpKr4pVrkwq0hacqGDBbz7mYGO2i1vN6l0EbkKto1x0N0c6/3bR6xqn 86NiykfvNwSg+YSpo/Gn4VuRsVE= X-Mailgun-Sending-Ip: 69.72.42.4 X-Mailgun-Sid: WyI0MWYwYSIsICJsaW51eC1rZXJuZWxAdmdlci5rZXJuZWwub3JnIiwgImJlOWU0YSJd Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n03.prod.us-east-1.postgun.com with SMTP id 5f6be38a722ceb032757767c (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Thu, 24 Sep 2020 00:08:42 GMT Sender: psodagud=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 91B3FC433F1; Thu, 24 Sep 2020 00:08:41 +0000 (UTC) Received: from th-lint-038.qualcomm.com (i-global254.qualcomm.com [199.106.103.254]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: psodagud) by smtp.codeaurora.org (Postfix) with ESMTPSA id 541DBC433CA; Thu, 24 Sep 2020 00:08:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 541DBC433CA Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=fail smtp.mailfrom=psodagud@codeaurora.org From: Prasad Sodagudi To: rostedt@goodmis.org, pmladek@suse.com, sergey.senozhatsky@gmail.com, gregkh@linuxfoundation.org, tglx@linutronix.de Cc: linux-kernel@vger.kernel.org, tkjos@google.com, Mohammed Khajapasha , Prasad Sodagudi Subject: [PATCH 2/2] printk: Make the console flush configurable in hotplug path Date: Wed, 23 Sep 2020 17:08:32 -0700 Message-Id: <1600906112-126722-2-git-send-email-psodagud@codeaurora.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1600906112-126722-1-git-send-email-psodagud@codeaurora.org> References: <1600906112-126722-1-git-send-email-psodagud@codeaurora.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Mohammed Khajapasha The thread which initiates the hot plug can get scheduled out, while trying to acquire the console lock, thus increasing the hot plug latency. This option allows to selectively disable the console flush and in turn reduce the hot plug latency. Signed-off-by: Mohammed Khajapasha Signed-off-by: Prasad Sodagudi --- init/Kconfig | 10 ++++++++++ kernel/printk/printk.c | 10 ++++++++-- 2 files changed, 18 insertions(+), 2 deletions(-) diff --git a/init/Kconfig b/init/Kconfig index d6a0b31..9ce39ba 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -699,6 +699,16 @@ config LOG_BUF_SHIFT 13 => 8 KB 12 => 4 KB +config CONSOLE_FLUSH_ON_HOTPLUG + bool "Enable console flush configurable in hot plug code path" + depends on HOTPLUG_CPU + def_bool n + help + In cpu hot plug path console lock acquire and release causes the + console to flush. If console lock is not free hot plug latency + increases. So make console flush configurable in hot plug path + and default disabled to help in cpu hot plug latencies. + config LOG_CPU_MAX_BUF_SHIFT int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" depends on SMP diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 9b75f6b..f02d3ef 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -2283,6 +2283,8 @@ void resume_console(void) console_unlock(); } +#ifdef CONFIG_CONSOLE_FLUSH_ON_HOTPLUG + /** * console_cpu_notify - print deferred console messages after CPU hotplug * @cpu: unused @@ -2302,6 +2304,8 @@ static int console_cpu_notify(unsigned int cpu) return 0; } +#endif + /** * console_lock - lock the console system for exclusive use. * @@ -2974,7 +2978,7 @@ void __init console_init(void) static int __init printk_late_init(void) { struct console *con; - int ret; + int ret = 0; for_each_console(con) { if (!(con->flags & CON_BOOT)) @@ -2996,13 +3000,15 @@ static int __init printk_late_init(void) unregister_console(con); } } +#ifdef CONFIG_CONSOLE_FLUSH_ON_HOTPLUG ret = cpuhp_setup_state_nocalls(CPUHP_PRINTK_DEAD, "printk:dead", NULL, console_cpu_notify); WARN_ON(ret < 0); ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "printk:online", console_cpu_notify, NULL); WARN_ON(ret < 0); - return 0; +#endif + return ret; } late_initcall(printk_late_init); -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project