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=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 05521CA9EA0 for ; Fri, 18 Oct 2019 15:21:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DB4FD222C3 for ; Fri, 18 Oct 2019 15:21:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2633014AbfJRPVU (ORCPT ); Fri, 18 Oct 2019 11:21:20 -0400 Received: from [217.140.110.172] ([217.140.110.172]:42406 "EHLO foss.arm.com" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S2389421AbfJRPVU (ORCPT ); Fri, 18 Oct 2019 11:21:20 -0400 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 CDC3AC8F; Fri, 18 Oct 2019 08:20:59 -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 0B4DA3F718; Fri, 18 Oct 2019 08:20:57 -0700 (PDT) Date: Fri, 18 Oct 2019 16:20:52 +0100 From: Sudeep Holla To: Yunfeng Ye Cc: catalin.marinas@arm.com, will@kernel.org, kstewart@linuxfoundation.org, gregkh@linuxfoundation.org, lorenzo.pieralisi@arm.com, tglx@linutronix.de, David.Laight@ACULAB.COM, mark.rutland@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, hushiyuan@huawei.com, wuyun.wu@huawei.com, linfeilong@huawei.com Subject: Re: [PATCH v4] arm64: psci: Reduce the waiting time for cpu_psci_cpu_kill() Message-ID: <20191018152052.GA10312@bogus> References: <04ab51e4-bc08-8250-4e70-4c87c58c8ad0@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <04ab51e4-bc08-8250-4e70-4c87c58c8ad0@huawei.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 18, 2019 at 08:46:37PM +0800, Yunfeng Ye wrote: > In case like suspend-to-disk and uspend-to-ram, a large number of CPU s/case/cases/ s/uspend-to-ram/suspend-to-ram/ > cores need to be shut down. At present, the CPU hotplug operation is > serialised, and the CPU cores can only be shut down one by one. In this > process, if PSCI affinity_info() does not return LEVEL_OFF quickly, > cpu_psci_cpu_kill() needs to wait for 10ms. If hundreds of CPU cores > need to be shut down, it will take a long time. > > Normally, there is no need to wait 10ms in cpu_psci_cpu_kill(). So > change the wait interval from 10 ms to max 1 ms and use usleep_range() > instead of msleep() for more accurate timer. > > In addition, reducing the time interval will increase the messages > output, so remove the "Retry ..." message, instead, put the number of > waiting times to the sucessful message. > > Signed-off-by: Yunfeng Ye > --- > v3 -> v4: > - using time_before(jiffies, timeout) to check > - update the comment as review suggest > > v2 -> v3: > - update the comment > - remove the busy-wait logic, modify the loop logic and output message > > v1 -> v2: > - use usleep_range() instead of udelay() after waiting for a while > arch/arm64/kernel/psci.c | 14 ++++++++------ > 1 file changed, 8 insertions(+), 6 deletions(-) > > diff --git a/arch/arm64/kernel/psci.c b/arch/arm64/kernel/psci.c > index c9f72b2665f1..77965c3ba477 100644 > --- a/arch/arm64/kernel/psci.c > +++ b/arch/arm64/kernel/psci.c > @@ -81,7 +81,8 @@ static void cpu_psci_cpu_die(unsigned int cpu) > > static int cpu_psci_cpu_kill(unsigned int cpu) > { > - int err, i; > + int err, i = 0; > + unsigned long timeout; > > if (!psci_ops.affinity_info) > return 0; > @@ -91,16 +92,17 @@ 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++) { > + timeout = jiffies + msecs_to_jiffies(100); > + do { > + i++; > 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); > + pr_info("CPU%d killed (polled %d times)\n", cpu, i); We can even drop loop counter completely, track time and log that instead of loop counter that doesn't give any indication without looking into the code. start = jiffies, end = start + msecs_to_jiffies(100); do { .... pr_info("CPU%d killed (polled %u ms)\n", cpu, jiffies_to_msecs(jiffies - start)); .... } while (time_before(jiffies, end)); Just my preference. Looks good otherwise. -- Regards, Sudeep