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=unavailable 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 76F91FA3735 for ; Thu, 17 Oct 2019 13:54:50 +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 4CB022082C for ; Thu, 17 Oct 2019 13:54:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="YmVrvSWp" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4CB022082C 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=QVBxMxzK0jdYdPirxV4U1Bzcwbw9esKI1UA6VhQTQnY=; b=YmVrvSWpHm0hWZ v1QiMkYGgWqWL/SasqUiZaYnTj4p/9A4+fZ2a8bU9reeuhJziqVzNMpWT1oeEvz9A8JiX4VVDBRpQ 2IXIYgjHuuw6C26rDd7/CoEwoznXpYJeLz2X0GVRbdS4cDhWDwEXTj+I+lSN0mFv51zECU1szmWze QNAX5obqy/GPSQ6+l/LhQuNgPSdorS5JiHDAUDzHJecftVsmeWlpVTvVircwEImceappvcOzNrC+S LHBkD/KEt+n1n21327U1Xv41T+Ols0it6mKPnWcmBi9l1tZVv6h0yMfR3dKhjse9ErSoVtYvWm3LK ZiTinMErmhn8hWrSwzMg==; 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 1iL6Ei-0006SB-DH; Thu, 17 Oct 2019 13:54:40 +0000 Received: from [217.140.110.172] (helo=foss.arm.com) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iL6Ef-0006QF-6v for linux-arm-kernel@lists.infradead.org; Thu, 17 Oct 2019 13:54:38 +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 E73811993; Thu, 17 Oct 2019 06:54:24 -0700 (PDT) Received: from bogus (e107155-lin.cambridge.arm.com [10.1.196.42]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2760A3F6C4; Thu, 17 Oct 2019 06:54:23 -0700 (PDT) Date: Thu, 17 Oct 2019 14:54:16 +0100 From: Sudeep Holla To: Yunfeng Ye Subject: Re: [PATCH V2] arm64: psci: Reduce waiting time of cpu_psci_cpu_kill() Message-ID: <20191017135416.GA26312@bogus> References: <18068756-0f39-6388-3290-cf03746e767d@huawei.com> <9df267db-e647-a81d-16bb-b8bfb06c2624@huawei.com> <20191016153221.GA8978@bogus> <0f550044-9ed2-5f72-1335-73417678ba45@huawei.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <0f550044-9ed2-5f72-1335-73417678ba45@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-20191017_065437_339566_DE2C41BE X-CRM114-Status: GOOD ( 23.59 ) 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" , Sudeep Holla , "linux-kernel@vger.kernel.org" , linfeilong@huawei.com, 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 Thu, Oct 17, 2019 at 09:26:15PM +0800, Yunfeng Ye wrote: > > > On 2019/10/16 23:32, Sudeep Holla wrote: > > 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 ? > > > When reduce the time interval to 1ms, the print message maybe increase 10 > times. on the other hand, cpu_psci_cpu_kill() will print message on success > or failure, which this retry log is not very necessary. of cource, I think > use pr_info_once() instead of pr_info() is better. > Yes changing it to pr_info_once is better than dropping it as it gives some indication to the firmware if there's scope for improvement. > >> - } > >> + /* 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 ? > > > msleep() is implemented by jiffies. when HZ=100 or HZ=250, msleep(1) is not > accurate. so I think usleep_range() is better. 1 ms looks simple and good, but how > about 100us is better? I refer a function sunxi_mc_smp_cpu_kill(), it use > usleep_range(50, 100). > Again that's specific to sunxi platforms and may work well. While I agree msleep(1) may not be accurate, I am still inclined to have a max value of 1000(i.e. 1ms) for usleep_range. -- Regards, Sudeep _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel