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=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 B0528CA9EB5 for ; Mon, 21 Oct 2019 07:47:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8612320830 for ; Mon, 21 Oct 2019 07:47:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727464AbfJUHr3 (ORCPT ); Mon, 21 Oct 2019 03:47:29 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:4693 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726480AbfJUHr3 (ORCPT ); Mon, 21 Oct 2019 03:47:29 -0400 Received: from DGGEMS414-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 855B6BB6E5538F4C3F30; Mon, 21 Oct 2019 15:47:26 +0800 (CST) Received: from [127.0.0.1] (10.177.251.225) by DGGEMS414-HUB.china.huawei.com (10.3.19.214) with Microsoft SMTP Server id 14.3.439.0; Mon, 21 Oct 2019 15:47:20 +0800 Subject: Re: [PATCH v4] arm64: psci: Reduce the waiting time for cpu_psci_cpu_kill() To: Sudeep Holla CC: , , , , , , , , , , , , References: <04ab51e4-bc08-8250-4e70-4c87c58c8ad0@huawei.com> <20191018152052.GA10312@bogus> From: Yunfeng Ye Message-ID: Date: Mon, 21 Oct 2019 15:47:17 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20191018152052.GA10312@bogus> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.251.225] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019/10/18 23:20, Sudeep Holla wrote: > 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/ > ok, thanks. >> 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. > ok, I will modify as your suggest. thanks. > 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 > > > . >