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, 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 DF44CFA372A for ; Wed, 16 Oct 2019 15:32:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BFD2720854 for ; Wed, 16 Oct 2019 15:32:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404984AbfJPPcb (ORCPT ); Wed, 16 Oct 2019 11:32:31 -0400 Received: from foss.arm.com ([217.140.110.172]:43458 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726332AbfJPPcb (ORCPT ); Wed, 16 Oct 2019 11:32:31 -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 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 Cc: David Laight , "catalin.marinas@arm.com" , "will@kernel.org" , "kstewart@linuxfoundation.org" , "gregkh@linuxfoundation.org" , "ard.biesheuvel@linaro.org" , "tglx@linutronix.de" , "wuyun.wu@huawei.com" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , Sudeep Holla 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-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9df267db-e647-a81d-16bb-b8bfb06c2624@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 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