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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 0C9A4C33CB2 for ; Mon, 3 Feb 2020 04:53:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DBD7F2073C for ; Mon, 3 Feb 2020 04:53:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727450AbgBCEuZ (ORCPT ); Sun, 2 Feb 2020 23:50:25 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:56856 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727317AbgBCEuY (ORCPT ); Sun, 2 Feb 2020 23:50:24 -0500 Received: from pps.filterd (m0098396.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 0134oH7H021102; Sun, 2 Feb 2020 23:50:19 -0500 Received: from ppma04wdc.us.ibm.com (1a.90.2fa9.ip4.static.sl-reverse.com [169.47.144.26]) by mx0a-001b2d01.pphosted.com with ESMTP id 2xxcmb8e0h-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Sun, 02 Feb 2020 23:50:19 -0500 Received: from pps.filterd (ppma04wdc.us.ibm.com [127.0.0.1]) by ppma04wdc.us.ibm.com (8.16.0.27/8.16.0.27) with SMTP id 0134nx48007166; Mon, 3 Feb 2020 04:50:18 GMT Received: from b03cxnp08028.gho.boulder.ibm.com (b03cxnp08028.gho.boulder.ibm.com [9.17.130.20]) by ppma04wdc.us.ibm.com with ESMTP id 2xw0y663ku-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 03 Feb 2020 04:50:18 +0000 Received: from b03ledav002.gho.boulder.ibm.com (b03ledav002.gho.boulder.ibm.com [9.17.130.233]) by b03cxnp08028.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 0134oHrZ62456292 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 3 Feb 2020 04:50:17 GMT Received: from b03ledav002.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1DFB413604F; Mon, 3 Feb 2020 04:50:17 +0000 (GMT) Received: from b03ledav002.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C86A4136051; Mon, 3 Feb 2020 04:50:16 +0000 (GMT) Received: from sofia.ibm.com (unknown [9.124.31.110]) by b03ledav002.gho.boulder.ibm.com (Postfix) with ESMTP; Mon, 3 Feb 2020 04:50:16 +0000 (GMT) Received: by sofia.ibm.com (Postfix, from userid 1000) id 19FAF2E2DB0; Mon, 3 Feb 2020 10:20:14 +0530 (IST) Date: Mon, 3 Feb 2020 10:20:14 +0530 From: Gautham R Shenoy To: "Naveen N. Rao" Cc: "Gautham R. Shenoy" , Kamalesh Babulal , Michael Ellerman , Nathan Lynch , Vaidyanathan Srinivasan , Tyrel Datwyler , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH 2/3] powerpc/sysfs: Show idle_purr and idle_spurr for every CPU Message-ID: <20200203045013.GC13468@in.ibm.com> Reply-To: ego@linux.vnet.ibm.com References: <1574856072-30972-1-git-send-email-ego@linux.vnet.ibm.com> <1574856072-30972-3-git-send-email-ego@linux.vnet.ibm.com> <1575564547.si4rk0s96p.naveen@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1575564547.si4rk0s96p.naveen@linux.ibm.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.572 definitions=2020-02-02_09:2020-02-02,2020-02-02 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 lowpriorityscore=0 priorityscore=1501 bulkscore=0 adultscore=0 suspectscore=0 malwarescore=0 mlxscore=0 spamscore=0 mlxlogscore=999 clxscore=1015 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1911200001 definitions=main-2002030037 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Naveen, On Thu, Dec 05, 2019 at 10:23:58PM +0530, Naveen N. Rao wrote: > >diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c > >index 80a676d..42ade55 100644 > >--- a/arch/powerpc/kernel/sysfs.c > >+++ b/arch/powerpc/kernel/sysfs.c > >@@ -1044,6 +1044,36 @@ static ssize_t show_physical_id(struct device *dev, > > } > > static DEVICE_ATTR(physical_id, 0444, show_physical_id, NULL); > > > >+static ssize_t idle_purr_show(struct device *dev, > >+ struct device_attribute *attr, char *buf) > >+{ > >+ struct cpu *cpu = container_of(dev, struct cpu, dev); > >+ unsigned int cpuid = cpu->dev.id; > >+ struct lppaca *cpu_lppaca_ptr = paca_ptrs[cpuid]->lppaca_ptr; > >+ u64 idle_purr_cycles = be64_to_cpu(cpu_lppaca_ptr->wait_state_cycles); > >+ > >+ return sprintf(buf, "%llx\n", idle_purr_cycles); > >+} > >+static DEVICE_ATTR_RO(idle_purr); > >+ > >+DECLARE_PER_CPU(u64, idle_spurr_cycles); > >+static ssize_t idle_spurr_show(struct device *dev, > >+ struct device_attribute *attr, char *buf) > >+{ > >+ struct cpu *cpu = container_of(dev, struct cpu, dev); > >+ unsigned int cpuid = cpu->dev.id; > >+ u64 *idle_spurr_cycles_ptr = per_cpu_ptr(&idle_spurr_cycles, cpuid); > > Is it possible for a user to read stale values if a particular cpu is in an > extended cede? Is it possible to use smp_call_function_single() to force the > cpu out of idle? Yes, if the CPU whose idle_spurr cycle is being read is still in idle, then we will miss reporting the delta spurr cycles for this last idle-duration. Yes, we can use an smp_call_function_single(), though that will introduce IPI noise. How often will idle_[s]purr be read ? > > - Naveen > -- Thanks and Regards gautham.