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=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 E1209C4360C for ; Wed, 16 Oct 2019 10:26:04 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 99482205F4 for ; Wed, 16 Oct 2019 10:26:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="HC0vi1CE" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 99482205F4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=lmdyBjfoSL5urkpzlqciVClz0EKEv8V0fcGdfb6lFNg=; b=HC0vi1CEj/Dc7x bbptM0ew8e3eT+ay7s826qnVhixb8iH2O6vO0ARDkDRwpJmMJkX5GwZEsnhVsLNX7a4QmOSysh7Eg rDD5KiIYxEZWyI+XeTj/YUlwPNBJMnd5YDkfU+e36lykunb56L02TG2uTx8GeA14pEojsgvGw4NAH GWIcCkpNmfWeMm2vOcovf98ddFohkiXrx2VZBb70UfeCOTBDFXLC1ayJ1eW+oDNv/Z5lRuMaJ6s6O pYGoDci8TzY4wLPUnlg61Algc6+N1cE7NwnyOfA9JLYpNzQ6FzHeitj0+CGt1H0dFjBAPvW3iWpdE 6LpFOXyOc6CaLxqyHvGw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iKgVE-0000wQ-0y; Wed, 16 Oct 2019 10:26:00 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iKgVA-0000vb-PY for linux-arm-kernel@lists.infradead.org; Wed, 16 Oct 2019 10:25:58 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BA6CB28; Wed, 16 Oct 2019 03:25:52 -0700 (PDT) Received: from bogus (unknown [10.1.196.42]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D936C3F6C4; Wed, 16 Oct 2019 03:25:50 -0700 (PDT) Date: Wed, 16 Oct 2019 11:25:45 +0100 From: Sudeep Holla To: Yunfeng Ye Subject: Re: [PATCH V2] arm64: psci: Reduce waiting time of cpu_psci_cpu_kill() Message-ID: <20191016102545.GA11386@bogus> References: <18068756-0f39-6388-3290-cf03746e767d@huawei.com> <20191015162358.bt5rffidkv2j4xqb@willie-the-truck> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191016_032556_875364_01E91F79 X-CRM114-Status: GOOD ( 20.36 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "kstewart@linuxfoundation.org" , "ard.biesheuvel@linaro.org" , hushiyuan@huawei.com, "catalin.marinas@arm.com" , "linux-kernel@vger.kernel.org" , linfeilong@huawei.com, David Laight , "gregkh@linuxfoundation.org" , "tglx@linutronix.de" , "wuyun.wu@huawei.com" , Will Deacon , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Oct 16, 2019 at 11:22:23AM +0800, Yunfeng Ye wrote: > > > On 2019/10/16 0:23, Will Deacon wrote: > > Hi, > > > > On Sat, Sep 21, 2019 at 07:21:17PM +0800, Yunfeng Ye wrote: > >> If psci_ops.affinity_info() fails, it will sleep 10ms, which will not > >> take so long in the right case. Use usleep_range() instead of msleep(), > >> reduce the waiting time, and give a chance to busy wait before sleep. > > > > Can you elaborate on "the right case" please? It's not clear to me > > exactly what problem you're solving here. > > > The situation is that when the power is off, we have a battery to save some > information, but the battery power is limited, so we reduce the power consumption > by turning off the cores, and need fastly to complete the core shutdown. However, the > time of cpu_psci_cpu_kill() will take 10ms. We have tested the time that it does not > need 10ms, and most case is about 50us-500us. if we reduce the time of cpu_psci_cpu_kill(), > we can reduce 10% - 30% of the total time. > Have you checked why PSCI AFFINITY_INFO not returning LEVEL_OFF quickly then ? We wait for upto 5s in cpu_wait_death(worst case) before cpu_kill is called from __cpu_die. Moreover I don't understand the argument here. The cpu being killed will be OFF, as soon as it can and firmware controls that and this change is not related to CPU_OFF. And this CPU calling cpu_kill can sleep and 10ms is good to enter idle states if it's idle saving power, so I fail to map the power saving you mention above. > So change msleep (10) to usleep_range() to reduce the waiting time. In addition, > we don't want to be scheduled during the sleeping time, some threads may take a > long time and don't give up the CPU, which affects the time of core shutdown, > Therefore, we add a chance to busy-wait max 1ms. > On the other hand, usleep_range reduces the timer interval and hence increases the chance of the callee CPU not to enter deeper idle states. What am I missing here ? What's the use case or power off situation you are talking about above ? > > > I've also added Sudeep to the thread, since I'd like his ack on the change. > > Thanks Will. -- Regards, Sudeep _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel