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=-8.2 required=3.0 tests=DKIMWL_WL_HIGH,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_SANE_1 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 2F48DFA372A for ; Wed, 16 Oct 2019 15:32:45 +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 EF4DD20854 for ; Wed, 16 Oct 2019 15:32:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="IFn2w77u" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EF4DD20854 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=0SITFAk42gbp0g3ILeifYFlX5Fb1ZrnqbRjXeyucVV0=; b=IFn2w77uE575Sj DJNBL9Q9paNGu4zXeINlHwFYNre/fyZpARAMwAdGyfy/RcXdsoZ9WQuVaDb9wyYSlhH9lRJNTh1FU NC2V6VjWcIF67KnW6IcoXZWe2mu3Zhxzk2H1KrASY4hc6YoHtBsPdLuBUTU1HCCoMQsALiYRnBsP7 A2fwCRVSrCO25/VgdSeYQUgr8oXXGxCWxFAH8CtBWp3WZGEQLVKFCstQO4Adt9ysnFmbOQioYRxtN Uu5DtD5Z3L3jYYtQnm2ZFuL8Z2WE8Sou/ImngU+kr/fZeyhvtIfEk5Qz11jA6kr9n8cvSUCFehELR 1vAKpjff8O3gHJQhisYw==; 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 1iKlHu-0001Qv-Al; Wed, 16 Oct 2019 15:32:34 +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 1iKlHr-0001Q4-Fm for linux-arm-kernel@lists.infradead.org; Wed, 16 Oct 2019 15:32:32 +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 47089142F; Wed, 16 Oct 2019 08:32:30 -0700 (PDT) Received: from bogus (unknown [10.1.196.42]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 86B693F68E; Wed, 16 Oct 2019 08:32:28 -0700 (PDT) Date: Wed, 16 Oct 2019 16:32:21 +0100 From: Sudeep Holla To: Yunfeng Ye Subject: Re: [PATCH V2] arm64: psci: Reduce waiting time of cpu_psci_cpu_kill() Message-ID: <20191016153221.GA8978@bogus> References: <18068756-0f39-6388-3290-cf03746e767d@huawei.com> <9df267db-e647-a81d-16bb-b8bfb06c2624@huawei.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <9df267db-e647-a81d-16bb-b8bfb06c2624@huawei.com> 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_083231_569877_99DB6458 X-CRM114-Status: GOOD ( 20.08 ) 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" , "catalin.marinas@arm.com" , Sudeep Holla , "linux-kernel@vger.kernel.org" , David Laight , "gregkh@linuxfoundation.org" , "tglx@linutronix.de" , "wuyun.wu@huawei.com" , "will@kernel.org" , "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 09, 2019 at 12:45:16PM +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. > > Signed-off-by: Yunfeng Ye > --- > V1->V2: > - use usleep_range() instead of udelay() after waiting for a while > > arch/arm64/kernel/psci.c | 17 +++++++++++++---- > 1 file changed, 13 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/kernel/psci.c b/arch/arm64/kernel/psci.c > index c9f72b2..99b3122 100644 > --- a/arch/arm64/kernel/psci.c > +++ b/arch/arm64/kernel/psci.c > @@ -82,6 +82,7 @@ static void cpu_psci_cpu_die(unsigned int cpu) > static int cpu_psci_cpu_kill(unsigned int cpu) > { > int err, i; > + unsigned long timeout; > > if (!psci_ops.affinity_info) > return 0; > @@ -91,16 +92,24 @@ static int cpu_psci_cpu_kill(unsigned int cpu) > * while it is dying. So, try again a few times. > */ > > - for (i = 0; i < 10; i++) { > + i = 0; > + timeout = jiffies + msecs_to_jiffies(100); > + do { > err = psci_ops.affinity_info(cpu_logical_map(cpu), 0); > if (err == PSCI_0_2_AFFINITY_LEVEL_OFF) { > pr_info("CPU%d killed.\n", cpu); > return 0; > } > > - msleep(10); > - pr_info("Retrying again to check for CPU kill\n"); You dropped this message, any particular reason ? > - } > + /* busy-wait max 1ms */ > + if (i++ < 100) { > + cond_resched(); > + udelay(10); > + continue; Why can't it be simple like loop of 100 * msleep(1) instead of loop of 10 * msleep(10). The above initial busy wait for 1 ms looks too much optimised for your setup where it takes 50-500us, what if it take just over 1 ms ? We need more generic solution. -- Regards, Sudeep _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel